I have a MY99 with standard 2-pipe outlet backbox. Are STi (STi5 as fitted to P1) boxes freer flowing and would it be worth changing to one? Or do I have to go to a Scooby or similar box to make it worth changing?

Just try it. I don't think there is a lot of difference other than the oulet is a single pipe as opposed to two peashooters.

You will find that there are loads available on here for very little money as most Sti owners fit aftermarket BB's anyway. I sold mine for £20 to a guy

They both have a 2 5/8" connection pipe just the STI is a single outlet rather than the twin. You wont get a lot of bhp (if any) but you can get a nice flat four enhancing growl if you change to an aftermarket pipe.

I cant wait for the first one to say I got 260bhp with just a back box change. Okay show me the engine dyno graph ;).

[Edited by chrisp - 11/22/2003 4:16:37 PM]