On my MY94 JDM WRX, which is totally standard apart from a HKS Super Drager exhaust and a K&N Panel Filter, i seem to have a problem on acceleration. The acceleration is far from smooth. There seems to be lumps and flat spots in the curve, to the point that when i was accelerating the other day my girlfriend thought i had bodged a gear change when i wasn't even changing gear.

This seems to happen under both normal and hard acceleration, but is obviously more severe under hard acceleration.

I did initially wonder about heat soak, then coil packs. But the problem is it sometimes pulls like a train, say one time in five, it drives excellently, then the rest of the time its cr@p and doesn't seem much more powerful than your average mondeo.

This can occur with or without octane booster, hot, cold, windy, calm, wet, dry, whatever. I always give the car plenty of time to warm up(minimum 10 minutes) and never really accelerate full-on(partially because i expect there is something wrong).

Any ideas?

Tony.