RPM's shootin up and down when I'm in Idle?
 

When I'm driving along and stop at a light in Drive, my RPM's shoot down than back to normal. Even if I'm stopped in reverse and even rarely while I'm in park. It increases the intensity when the A/C is high. No loss in power I do believe I'm wondering if its a fuel problem? Any suggestions please give me a holler. 2008 Chevy Silverado 1500 4x4 Z71 V8 5.3L Active Fuel Management ( Not FLEX) Thank you

Whats the rpm range?