Im putting on headers and a gibson exhaust to try to pick up some milage but i was wondering my truck has 84000 but the 4.2L engine and i hope the cats should only have about 40000 on them. how long do cats last? And since i need them in MD for emmisions whats the eastist way to replace? Like does someone make a direct high flow kit of do they need to be universal and welded together. when i do the exhaust or the cats should i also do the O2 sensors cause they aint cheap for all for of them things.
Adam

 

Hey Adam, check out the post for "How much louder" I think alot of your questions will be answered there. Yes, you can replace with some hi flow cats and still pass emissions. I just replaced the stock 4 cats (only had 15k on 'em) and replaced with 2 Magnaflow hi flow cats. I passed inspection and emissions just fine. Hope that helps some