Message: Just installed a Hughes stage 1 intake manifold on my '99 5.2. No problems except that it has a high pitched whistle while idling and at steady speed cruising. Gotta be vacuum but have sprayed WD40 on everything and pitch did not change. Tightened, removed, checked, reinstalled and tightened everything and it sounds the same. Some ideas please.
Subject: HELP! Another big problem.