Anybody have/had an idle issue? It idles fine at a cold startup, however when the engine warms up after a drive; when at a stop in first or in neutral it fluctuates between 900 and sometimes gets down to 400/500 and then jets back up to normal idle rpm. Done some research but have seen many different causes. It currently has a tune and a JLT intake on it as well. It's an 04 with 44k miles on it