I'm looking at getting a custom exhaust done up at a local shop but I was curious about the stock exhaust having an air bypass valve (could be wrong name) that came from the stock main catalytic converter and up to the engine. Is there any harm in plating this off and not having it on the custom exhaust? I already have part of the ACV plated off incase that is relevant. Also how many high flow catalytic converters should I get him to install if i'm doing 3" the whole way? stock there are 2 but with a high flow performance cat will 1 be enough to still pass emmissions?

any feedback will help i'm self taught when it comes to rotary so I haven't learnt it all yet.

 

If your s4, you need it for your 5/6 aux's to work. If your s5 you can just get rid of it.

 

so i can block off my air bypass valve. if i do so will my 5th an 6th aux port still work

 

ya I am S5, i'm just worried about getting rid of too much of the emmission control stuff and then having trouble passing

 

If you have emissions there, keep it. It pumps fresh air into the exhaust.

philly - I don't think you can. Unless your talking about the split air pipe into the exhaust.

 

run a high flow converter, everything will stay emissions legal and there wont be any difference in power in a NA car

 

I don't have an NA it's a JSpec TII engine, i'm still on the fence about just plating it off or not