The engine is modified with big cam, heads and so on, the engine and transmission tune have also been modified. The problem is when decelerating to a stop in drive as the car downshifts into 2nd and 1st gear the engine rpm goes up just just enough to cause the car to jerk forward which can be irritating and dangerous. I don't think it is the transmission shifting I think the throttle is making an adjustment. It does not happen in sport mode when using the paddle shift. Ideas anyone?