[Paparoach]

First off a dual exhaust would only be good if you wanted to change the look of it, it would not change performance at all on the little 4 cyclinder. Many people believe that it is not necessary to go over 2.25 inch exhaust on an NA car. Dual exhaust are used generally on V8 when there are two headers.

70mm throttle body is definately not worth it and the 65mm is overkill in most cases. I would only move to the 65mm myself until after changing my cams and gears. 70mm is only for use when pushing big big numbers. The best and cheapest way is porting your own...just don't get Dan to do it unless you have two days.