Originally Posted by
Coheed clean her up. Get the preventive maint done. Then get rid of the factory exhaust. It sucks. Keep it quiet though, you don't want anyone thinking it is actually fast. Cause it aint.
A stock SE-R exhaust would probably do wonders, and be way more capacity than would be useful for a GA. And it would be quiet and fairly discrete.
The OE muffler is of excellent design, of course it produces back pressure to reduce noise, but only above where non cammed SR20DEs poop out, or after 6500rpm. With or without a cat the stock muffler is producing results close to the turbo muffler, but MUCH quieter. The OE muffler seems to start increasing back pressure at about 5500 rpm on up. Nissan did their homework in designing that muffler, the back pressure buildup corresponds very nicely with the stock engine performance characteristics. A stock SR20DE starts to choke after 6500rpm, the OE muffler ramps up 1 or 2 psi till about 6500rpm where it sharply increases to its maximum.
^^From here:
General Info on SR20DE exhaust systems