Update:  So this issue as discussed ended up having nothing to do with a Misfire.  It was a quick shudder from the torque converter that can feel just like a misfire.  The confusion came about as multiple issues happened at the same time.  The valvetronic motor needed replacing and a coil pack died. The main issue is a shudder caused by the GM made torque converter.  A common failure in all vehicles that use this gearbox.  Usually occurs when the gearbox fluid is old or low. The fix:  A tra