When I removed the screen from my TB it was totally clean. The car is a '99 with 47K miles. With my 9" K&N and 3.4" pulley the car is noticeably faster. I guess I couldn't really feel a difference in power when I first removed the screen, before the pulley upgrade. I just want maximum flow so I'm gonna leave screen out.
__________________
3.4" SC pulley, 9" K&N cone, 180 T-stat, Dynomax cat-back, 30% tint
