I recently installed a super charger (wynjammer) with a reprogrammed PCM on my 07 Sierra. I'm running the 4.3L with a 5 speed M/T. When I disengage the clutch with a cold engine (i.e. downshifting approaching a stop) the engine revs up 700-800 rpm's. After the engine reaches operating temp it settles down and runs fine. I've checked for vacumn leaks and everyhting is fine. Can any one share some information on what might be happening and if there is anything I can do about it. The company suggested that I let my truck idle until it warms up.