lambo12000

Hay guys so lately I've been noticing this crackling sound in the morning when I'm pulling out of my neighborhood (almost like liquid evaporating) and I start to take my foot off of the gas at about 20-25 mph. This sound only occurs after the truck has been sitting turned off for about an hour or two, and doesn't occur at speeds > 35 mph. It really only happens when I start to accelerate from a complete stop, but does not happen at a complete stop after driving for about 5-10 minutes. (This might be a completely different problem) I've also noticed while my AC is on and I'm sitting idle, my engine will down rev below its idling point for half a second. Not sure if that problem has anything to do with the noise, but I would also like to get some feed back on that issue as-well. It would be great if I could get some ideas of what could be causing the sound/AC problem and some easy ways to test for it. It would be really great if I could fix these problems especially without having to take it to a mechanic. (03 2500 Silverado 6.0L Vortec)