could your belt possibly be slipping when you put hte extra power from driving through it, or to say its gripping at idle and actually spinning faster or more constant than while driving due to slippage.
Just a idea altough I doubt it since its a newer vechile
i dunno, all i know is that steve meade is running there product in his tahoe and now his caddy and he has nothing bad to say about it. and if steve meade thinks its good, it sure should be