Whistling 2000 Jeep Cherokee

My Jeep has a high pitch whistle coming from the engine that comes and goes. Seems to go away when accelerating and comes back when coasting or idling. Doesn’t do it all the time. Thanks

Sounds like a vacuum leak, vacuum is low when accelerating and higher at coasting or idling. Wave an unlit propane torch around suspected areas and see if the engine speeds up or smooths out.