Ok I have a 2004 Screw 5.4 4x4. I called my local shop the other day tring to a quote on a new exhaust setup. I wanted to cut all of the cats off if possable. The guy at the shop told me I could not take off any of the cats without causing problems. I don't have to worry about emissions here. Is there anyway I could remove the cats or do I need 2 hi flow cats?

 

you can always gut them and put them back on, then the truck will pass a visual inspection if nothing else. once they're gutted, they pretty much become straight pipes

 

cats are required in all 50 states. Convert to hi-flows.

 

So I can put 2 hiflow cats and it won't trigger a check engine light? Can someone point me in the direction on the cats I need?

 

Get 2 magnaflow high flow cats in place of your 4. It will run better, cleaner, and sound better.

 

Just remove the rear two cats and leave the front two. It'll sound a lot better and give you a few rwhp. The 2004-2005.5 F150s came with four cats compared to the 2005.5+ F150s which have only two.

 

Agreed. I may be following that route. Cutting the rears will give no CEL because they act more as resonators.

If you would prefer the two hi-flows replacing all 4 ( and find a shop that would do the work ) part # 94306 will work.

 

The stock front and rear cats perform different functions. If you cut off the rears, it may change the O2 reading of the post-cat HEGO sensors. Meaning that aside from breaking federal law, no increase in performance and dirtying up the air the rest of us breathe, you will also have stored error codes, a MIL light and a guaranteed inspection failure. If you're determined to replace the stock ones, go to high-flow 3-ways. You gain performance, stay legal and don't increase pollution.

 

I have already found a shop that will cut them off. But I will probably go with hiflows. Thanks for the help guys.

 

Cutting the rear cats will net you a gain of 2-3 rwhp. The 02 sensors are in front and behind the front set of cats. Therefore it's not going to effect any of the tuning. There will be no CEL or stored codes, etc. I also doubt you'd be doing everyone a disservice by polluting the air you breath. I'm willing to bet the front cats are more than enough to keep the pollution down to tolerable amounts.