I've been going crazy trying to figure out why my truck is doing this. It only idles loud and rough when up to temperature, stopped at a light, or in park. So far I have put new spark plugs and wires, I've changed the oil to synthetic, I checked for vacuum leak there's no leak, I cleaned out the iac, I cleaned out the throttle body, I've tried using better gas. This does not affect the performance of my blazer at all it drives great the oil pressure is right in the middle, the temp gauge is in the middle, and it doesn't jump at all in rpms when stopped it stays normal and low. Someone please help me fix this!.