I was wondering if it's bad for the engine if i got a high flow cat that wasn't emissions friendly, and then when time comes to smog, i put the old one back on for emissions. If i do this year after year, will it harm anything in my car?

 

No, its safe for the engine, just not for you me. Its not worth swapping them out yearly. You wont gain jack.

 

i didn't mean every year, just every other (For Cali smog certificate). You really dont think i would gain any horses???

 

what else is done to the car?

 

not much, just short ram intake, magnaflow muffler and that's about all the performance mods. Why?

 

with those mods you will not gain anything at all. if you had boost or nitrous it may help but for NA your just wasting your money.

 

Point taken. Thanks!