What is it and how do I put it in

 

A straight pipe is a pipe that replaces the DPF/CAT pipe currently on your vehicle. Plenty of information on the forums explaining how to remove the exhaust system and replace with a delete pipe.

Also, you MUST have a tuner of some sort or your vehicle will go into limp mode if you install a straight pipe or delete pipe.

 

It's exactly what it says. Straight pipe. No emissions components. DPF, DOC, Muffler. Nothing but pipe.

 

What goes in to taking everything off

 

DPF & DOC requires the disconnection of 4-5 sensors, a few bolts and removal from the exhaust hangers along with a DPF delete capable tuner. The muffler is welded in so best bet is to buy a new system. Either DPF back, downpipe back or turbo back.

 

The Downpipe back is probably your easiest.

 

Is this statement 6.4L specific?

 

I have never heard of it being a "must" to have a tuner for a straight pipe exhaust system to work correctly.

 

Also, what is this limp mode that you speak of? I am interested in this. Thanks.

 

No. Most first generation EPA approved diesels use DPF technology. The 6.7 uses DPF but adds another component to help with the breakdown of exhaust gasses (DEF). Because the process involves the vehicles PCM, it requires a tuner to modify that process.

A gas vehicle can be "straight piped" by removing tha catalytic converter and muffler.

 

"Limp Home Mode" is just that. Your vehicle goes to a very limited power level to allow you to either get home or at least drive to a safe stopping point in an attempt to prevent major damage or more damage than has already occurred.

 

Depends on the year of the vehicle. Pre 2008 Ford trucks did not have a DPF so they could just have a straight pipe put in place of the CAT pipe going out toward the rear. Ford truck model years 2008 to 2010 have the DPF in place to capture the soot expelled on the exhaust stroke. It is burned out by injecting diesel on the exhaust stroke to clean the DPF during the regen cycle.

Ford truck model years 2011 and newer also have a DEF feature as RM2738 mentioned which is used instead of diesel to help burn out thee soot in a DPF during the regen cycle.

Pre DPF trucks did not require a tuner to go to a straight pipe as the computer did not control the emissions components on the exhaust system. When they introduced the DPF they also included special programming to activate and deactivate the regen cycle when it detected that it needed to be cleaned.

If you were to straight pipe a 2008 model year truck or newer, your truck would go into constant regen cycle and eventually limp mode without the necessary programming that a tuner performs.

I think RM2738 covered this nicely.