i have a 2002 5.4 4x4 and want to put true dual exhaust on it, and have it exit like a lightning. i live in florida so emissions testing isnt really a problem, and have seen plenty of mustangs around with off road h pipes, so i was wondering if i could cut off the cats and replace them with just 2.5 inch pipes. i called around and have heard from some that itll mess with the trucks computer and will make it run worse, and from others that there will be no performance problems at all - just gains - and all you have to do is get mil eliminators to turn off the check engine light and everything will be fine. im wondering if anyone has this set up and can help me figure out how my computer will respond to the change. if i cant take them off, can i replace the 4 stock cats with 2 high flow ones and still satisfy the computer?

- goose

 

Go for the high flow cats. You will still be legal and get the gains in performance your'e looking for. TroyerPerfomance.com has everything you need. It is against federal law (all 50 states, whether enforced or not) to remove your cats.

 

I guess the desired end results is in order here.

Are you looking for performance, or noise ?

Removing the cats, yes you'd need something like a Casper Electronics MIL elminiator.
If you are doing true duals, use a X pipe, not a H pipe.

Make sure the system is 100% 16 ga 304 SS pipe, not aluminized ( need to keep the xhst gas temp up, aluminized allows it to cool too much ).

You did not note a muffler choice, if any.

Even replacing the stock Cats ( unless plugged ) is not that great of a gain without long tube headers, and a chip programed for the change in flow.

If you are after the true duals for performance gain over a cat back ( i.e removal of the factory Y pipe ) then just leave the stock cats alone, and have the system cut at the factory Y pipe and start from there.

If you have all the more pedestrian mods done ( intake, chip, E-fans, pulley set ) and you want more out of it, then look to long tube headers, high flow cats, X pipe and dual SI/SO mufflers. ( don't forget to reburn your chip ).

If you are looking at this before the other mods, your cost per HP is going to be out of wack. You will spend 600.00 plus ( on a SS system ) and get a bit of return out of them, where putting on the E-Fans is about 400.00 and nets more usable HP at teh ground.

Sorry that is alot of pontification, I have sigs turned off, so I don't know what you have done so far, to make more then a SWAG at which order you should do things in terms of HP/dollar spent. That is if this is a HP mod, not just a sound mod.

Let me know how far off base I am on this.

 

ive been looking at headers, and the only ones that show up for my truck on sites are the shorty headers. i talked to a friend who said that for the money, they do not provide that much gain over the stock ones to begin with, so i was just going to leave them until i happened to one day have enough spendable money. are there any long tube headers out there thatll fit a 5.4L 4x4? if so, im still not sure that would provide even enough room for two hi flow cats - the current position for those cats is almost directly beneath the stock header connection. i have two 40 series flowmasters and an x pipe and my friend who has a muffler shop is going to set me up with splitting the y pipe and finalizing the back half of the system.

- goose