I have a 2004 FX4 5.4L regular cab. I have been told by several people that cutting after the cats and running truse duals will produce a problem indicator light because the cats won't work properly. My exhaust guy says that he installs them all the time with no problems. Which school of thought is correct here? Anyone running true duals on this engine? Thanks.

 

The converters should still work fine. The only possible problem I can see is with the O2 sensors, but I don't know why they wouldn't work the same as before.

 

I'm not yet, but I plan to. The issue with the cat backs currently available is that they bolt on where the factory muffler bolts to the factory Y coming from the cats. The factory Y has two 2 1/2" pipes joined into one 2 1/2" pipe. Bolting a 3" or dual exhaust system onto a 2 1/2" Y pipe doesn't make sense to me.

I intend to have either a 3" single or dual 2 1/2" system welded on to the factory pipes right in front of where they come together. If I get a dual system, I'll get them both run down the passenger side of the truck and out the passenger side behind the rear wheel. The drivers side of the truck is blocked by the gas tank. Also, I don't want rear exit duals because I regularly tow things I'm fairly fond of.

The only issue I haven't researched is whether there are any O2 sensors attached in the section of exhaust I intend to have disgarded. If so, I'll have the muffler shop include them in the new system.

As long as you don't eliminate any of the factory O2 sensors, you shouldn't have a problem.

Enjoy.

 

I have true duals on mine and have never had any engine light come on and it runs and sounds great

 

me too... I have true dual, with no problems. Sounds great.. No lights.

 

I had 3" dual exhaust put on with no problems.

 

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