It could be oil in the system. Basically when you give gas hard or romp on it the air picks up the oil in the system and pushes it through the motor and burns it off. Is it a quick puff of smoke or a continuous stream of smoke once you floor it?? btw, i'm assuming you are the person i ordered the head gasket set in with the valve seals. Let me know if you still need it, i need to return it if you dont!