Quote Originally Posted by Andrew_99GTP View Post
Did you get the one for single or dual exhaust? Do you think the single O pipe setup would increase gas mileage in my GS?

I got the one for the dual. I don't know how big of a mileage increase you will see but you will really feel it with the power. My buddy has a 1999 GP and he has just the single O pipe and when he gets on it you can really tell. I would say you will only see about 1 MPG difference. Every car is different though.