I installed a K&N drop in filter today and it has made a pretty significant difference in the performance. More than I expected and this is my 3rd boosted car now. I think the problem is the sport uses the same airbox and air filter as the 2.0L I-4 engine. The engine sounds louder, noticeable louder which at first made me think I didnt clasp the air filter box properly all the way. I think this should be the first mod everyone does, the butt dyno was very surprised.