99 Ranger, 3.0 V8, PSPB, air, cruise. This has not happened often enough to describe too explicitly but sometimes shortly after I shut the engine off I'll hear a whistling noise -- it's short in duration and 1 or 2 whistles and it sounds exactly like someone whistling a low note. It appears to be coming from under the hood on the right side. The location is hard to pin-point because if I try to listen for it, it probably won't happen. Anyone experience this ?