OK, i just installed my high flow cat today and cant figure out how to hook up the little hose that went to the stock cat. Its a small line with a flange with two bolts. What exactly does it do? Any ideas? Forgot to take a pic of it while it was on the lift. Thanks...

 

That's the air injection port. Basically it comes from the air pump via the air control valve. If you have no port on the HF cat for it, some think you should get a shop to weld in a bung for it, as without the air, they say the car will not pass emissions.

 

Does it really matter? Where i live i know several people and its not a big thing, passing emissions. I was just wondering if it would damage my car at all. Im going to try and get someone to weld the one from my stock cat onto this one.

 

Well, that's a huge debate. It's possible that there won't be enough O2 to burn off all the emissions at low rpms (which is where the airpump helps out) and that could cause premature failure of the cat. However, there really isn't a lot of proof of that.

What will happen is that until the cat has warmed up, your exhaust will smell almost as bad as a midpipe without the airpump line running to it.

 

Thanks i appreciate it, i wish i was as smart as you guys!!

 

It's not smarts, just experience