The car is a 3.4L 2005 Impala. I noticed that when the car is in park and I rev the RPM's up, it will suddenly bogg for a split second, then speed back up, then bogg again, etc. I don't know exactly what RPM's I'm running at because there is no tach, but i know its not high enough to be hitting any governor or anything like that. Im not running it fast enough to damage it. MY estimate would be around 4000 RPM's- just a guess though. Anyone have any idea of what to starting looking at?