Ok, I have a 2004 Lariat 5.4. Do I have 2 catalytic converters, or 4? And if I have 4, are the rear two A) safe to cut off? B) true cats, or pre-cats?

 

If you have 4 the rears are the cats, the fronts are pre-cats. If you just want to cut off the rears and not replace them you may start throwing codes from the rear O2 sensors. So you would then need to either get MIL eliminators to fool the computer or you can get a tuner to just turn off that part of the program to ignore the signals from the rear O2s. But you may have issues passing emissions test if they have them in your area.

IMO, cut off all 4 cats, replace with 2 Magnaflow Hiflow Universal cats. Sounds better. Also if you take it to a shop make sure you insist you get your old cats back, then take them to a local scrap metal dealer and get some good $ for them. I got $200 for my four 11 year old cats a few months ago.

 

Cut the rear two off, and just leave the fronts, they will flow just as good as high flows and costs far less to do, and you can sell the back two and pay for the work. The trucks run fine on just the front two, and usually don't set the CEL.

 

i've been thinking about doing this eventually. are there any gains, or is it mostly for the sound?

 

Minimal torque gain, and much more sound gain.

 

yep dude you got 4 cats chop the rear (big ones) off and youll be good 06+ only has 2..and their massive!!!