My M50, when it's under load (usually when you gun it in the upper gears) makes this soft whistling sound. It's not very noticeable unless you are listenting for it. The best way I can explain it is one of the little bird whistles we had when we were kids that you filled with water, but with a deeper more even tone. It only last a moment or two when you first twist the throttle under load. Any ideas? I have an open element (thunder kit) but I haven't noticed this sound until just recently, and I haven't changed anything in the last 500 miles.
01-30-2006, 10:48 PM
Engine makes a soft whistling sound under load 
