I was wondering if I were to cut the pre-cats would I loose torque or HP? I really like the sound but I dont want to sacrifice power.. The plan would be to cut the pre-cats and put a pipe there.. Oh and another question, would it make the check engine light turn on?

Thanks!!

 

I also would like to know this, i'm in the process of trying to make my F150 a little louder.

 

cut out your rear ones, it gives the exhaust shop less to do (less bending) so that will keep that cost down, plus the rear ones are the restrictive ones, the pre-cats are pretty much high-flows. btw, mine didnt throw a cel after i cut em out so i didnt have to get an O2 sim. but ive heard of people who have so it probably just depends on the truck. i couldnt tell than there was any loss in power, but there was a big gain in tone and loudness.

 

If i need to get O2 Simulators where would i get some?

 

You can get them on ebay some for a mustang will work. You can get some that are plug and play or cheaper route you can get some that wires in.

 

If you cut the rear cats will it still pass emissions? Hopefully it won't matter i have 20% tint and my buddy can "supposedly" get my truck passed somewhere.

 

Nobody knows if it will pass inspection with just the first set of cats?

 

you should be able to pass inspection with fronts gone, and rears in *except maybe in cali

I gained alot of top end power (HP) breathability etc. Felt about the same on bottom end, after i gutted my "precats" or first pair. Just make sure you dont have exaust leaks like i have. Also will make your exaust more "poping" sound. Unless you weld a pipe inside the cat housing. B.c the pressure will build up and release inside the cat housing, and make it pop alot when engine breaking or revving.

Also no CEL or engine problems if you take out the fronts, and leave the rears...
-Patrick

 

depends where you are. If there is a visual inspection then you're at the mercy of the mechanic noticing... if its just an OBD check then the test is only checking for codes.