My car has about 7k miles on it since the rebuilt engine was put in it and is smoking some. When the car is cold in the mornings when I start it, it will smoke for about 5 to 10 seconds which is prob not unusuall considering it has straight through exaust. The smoke is whiteish grey and is not coolant because the coolant seals went out on my old engine and i know what that smoke smells like and this is compleatly different. After about 10 sec of smoking it will stop and I can let the car sit for 20min at idle and it will never smoke a drop. I can drive it without getting on boost and it will never smoke. But if i get on boost a few times and then come to a stop it will gradually start smoking after about 2min of idleing. It doesnt blow any out while driving or when I first come to a stop. The smoke really doesnt smell like oil smoke. Could it be just running really rich at idle after getting on boost since I dont have any cats???? The prob actually started right after a replaced the maincat with a midpipe. Any advice?