joe603 wrote:It could be nothing...or it could be more expensive. Our cars have variable timing and it changes with the engine temp. On a cold engine, you'll notice more engine growl. This is all controlled by the computer.
Good news is that if it was a major problem, you'd probably have some indicator lights.
Check around for vacuum leaks from the AC belt change (they may have disconnect items to get to it).
johnparkyourcar wrote:Its probably just a vacuum leak somewhere. Mine does that too so i have to rev it a little bit everytime i start it. But I know its from my plenum spacer. I'm just too lazy to fix it...
+1 This is probably the issue. I've also seen dirty Throttle bodies do this.
Let the car idle and listen for and air leak sounds.