This issue has been a hot discussion topic for several weeks now.
For everyone's reference and use, I am going to list step by step instructions on the disconnection of the EGR system and removal of the EGR backpressure throttle plate (this throttle plate is only present in early 03 builds, and all 2004 builds; This is in reference to the ENGINE build date, not the trucks; if this does not apply to you simply skip over it and disconnect the EGR only)
Here are two earlier posts I made about its effects on my motor-
Originally Posted by PSD 60L Fx4
Since you have a 550, I will assume you will doing a large amout of towing. If I may, I would advise you to unplug the EGR valve on your motor. The valve is located directly in between the large black cylindrical oil filter and 90 degree aluminum intake elbow/throttle body on top of the motor. It is a small black cylinder directly on top with a 4 prong wire harness connector going directly into the top. Just pull the plug. This issue has been debated quite a bit on this site; some will tell you it helps performance and mileage, and some will disagree. This is my experience, good and bad.
Upon disconnection, I noticed a small to medium decrease in the turbo spool time (ie, less lag) under partial throttle, lower rpm conditions. This modification will not affect the motor at higher rpm's under heavy load, as the motor lacks the backpressure to trigger exhaust gas recirculation under these conditions. The reason for the partial throttle enhancement is this - the EGR valve pulls exhaust gasses out of the passenger side uppipe and recirculates the gasses back into the intake to reduce engine emissions. This has a negative impact on power in two ways. First, the exhaust air is much hotter than the air from the compressor side of the turbo after it is intercooled. The EGR system has a cooler on it, but from all literature i have read the gasses from it are still an average of 150 to 200 degrees hotter. Hot intake gasses negatively impact performance. Foremostly, however, is the fact that the gasses are drawn from the uppipe. The lost quantity of gas is that of which COULD be spooling the turbo; therefore by disabling the valve, 100% of the exhaust air is being put through the turbocharger, thereby reducing the time it takes to spool up.
Do not expect any miracles from this, however IMO it is worth the total of 10-15 seconds it takes to pull the plug on it. Doing so will generate two Diagnostic Trouble Codes in the PCM - P0400 (Exhaust Gas Recirculation Flow Error) and P0407 (Exhaust Gas Recirculation Sensor A Circuit Low). Neither of these codes will trigger the check engine light, and can easily be cleared with a tuner, scanner, or by simply unplugging the battery. As for gas mileage, I really have not calculated, but the overhead lie-o-meter seems to have shown about a half mile to the gallon gain.
I have driven about 3000 miles with it unhooked now. According to the 6.0 Bible, the default position for the valve is closed. Therefore, when the engine is shut off, the valve will be closed. Unplug the valve with the engine off and it will not open again until it is plugged back in. Alot of people I have talked to notice very little or no performance gain from it; I apparently was a lucky one and experienced a middle-of the road gain. I suppose its just worth a try; if you try it and dont think its worth it, it is very easy to put back the way it was. As for the engine running cleaner, I have noticed that there is very little or no oil in the boost tubes or intake elbow after unplugging it.
Here is a quote pulled from FredsF250TD in another thread...
Originally Posted by FredsF250TD
I just bought my wife a new VW Passat 1.9 TDI last Saturday. While trying to track down the 5w40, VW 505.01 spec synthetic oil VW says HAS to be used in this motor, I ran across a website that has a EGR bypass kit for the TDI. They had pictures of the amount of soot that builds up in the intake and the EGR. I mean these things were AT LEAST 3/4 clogged compared to the pics of a clean intake. They did not say how many miles it took to do this, but frankly I don't care. It was a mess, and they said it was all due to the EGR. I know, we are talking two different engines here, but they are both diesels with EGR systems.
On most 03's you will not receive a performance gain, as mentioned earlier. However, in all build dates, by disconnecting the EGR, you will clean up your intake air by preventing the recirculation of engine carbon, ect. Theoretically this will increase the life of both your oil and engine.
The EGR is located on a small black cylinder (the black cylinder is the valve itself) right between the oil filter housing and intake elbow on top of the motor-just pull the plug. If you cannot find the location of it, first check the links above. Second – under the hood of the vehicle, look direcly to the center of the top of the motor. You will see a large black cylinder sticking out of the top of the motor; it is the largest object front-side of the turbocharger. Direcly in front of it will be a smaller black cylinder, with a 4-wire weatherpack connector on top. Reach down, pull the tab on the backside of the plug, and remove it. This will disconnect the EGR valve. (Ensure that the switch to the vehicle is off before pulling it, the vehicle must be off to ensure the valve is closed. Otherwise, it is possible to lock it in the open position.)
The throttle plate is a slightly more involved process to remove. REMEMBER, this is not necessary for later 03 build dates; once you get the elbow off there will be no plate. However, for anyone with a set of sockets, it is simple. Here are the tools you will need – a 3/8 drive ratchet, a 3/8 extension bar (preferably a fairly long one), an 8mm socket, a 10mm socket, and either a 9mm socket or a flathead screwdriver, depending on the build date of the engine. To begin – remove the clamp holding the boost tube to the engine. The boost tube comes up from the bottom of the right side of the front of the motor, over top the motor, and into the elbow. The clamp will either be located on a piece of flexible rubber hose (03 build) or on a rigid black plastic pipe (04 build). For 03 build, there will be two clamps, remove the one closest to the aluminum elbow. Remove these and slide the boost tube over out of the way. The elbow will have 4 bolts holding it onto the throttle body assembly. Three are 8mm; the front left side bolt is a longer, 10mm bolt. Remove these, and pull the intake off. In either the groove on the bottom side of the intake or the top side of the throttle assembly, there will be a large rubber o-ring. If possible, leave this ring in one of the grooves. If not, lay it to the side and DO NOT LOSE IT. When looking into the throttle assembly, you should see a large butterfly valve mounted in the throttle assembly. (ONCE AGAIN, if you do not, you have a late 03 build; begin the reassembly process) On both the right and left hand side of the throttle assembly you will see black boxes with wires leading into them; the left hand side is the throttle body servo motor, the right hand side is the throttle plate position sensor. It is not necessary to do anything to these. To remove the plate, you will need a #10 torx driver. There are two small torx screws holding the plate to the throttle plate mounting crossbar. Rotate the plate to the SHUT position and loosen these screws. Before removing the screws totally, ensure that you have a magnet to pick them up with. YOU MUST NOT DROP THE SCREWS INTO THE INTAKE. Remove the screws with the magnet. Rotate the plate back to the open position, and pull the plate straight up to remove it. For reassembly, start with the rubber o-ring between the throttle body and the intake elbow. If the motor was hot when you removed the o-ring, soak it in water for 30 seconds to cool it down; as if it is hot it will not properly fit back into the slot. Be sure the o-ring is properly seated and place the intake elbow back on top of the throttle body, ensuring that the holes are lined up. The larger of the 4 bolts goes back into the bottom left hand side. Retighten. Then, slip the boost tube back over the lip on the intake elbow. Retighten the clamp holding the tube on, and ensure that it is quite snug, BUT DO NOT STRIP IT OUT. If you have an 04 motor, do not slide the plastic tube all the way back to the end of the lip of the elbow. Slide it most of the way and snug it up lightly; wiggle it until it seats and then fully tighten. Start the motor and ensure that you cannot hear any air noises, ect. Presto.