Mine does it too. The PCV system maybe at fault, and if you hunt for a bit on the board you will find it's easy to look into yourself. This was not the problem with mine however, as I have ~63% leakdown on two cylinders. This has not stopped me from enjoying the car, I change those two sparkplugs twice a year and I'm all set. The fact that it does it when yoou get on it hard would lead me to believe you'vve a similar case to mine. (It used to piss me off really bad until I got on it good approaching an 850Csi on a freeway on ramp. He got into his car and I saw the same smoke....)