Ok, so I decide to go for a short drive with the cover off the air box and see what that is all about. Sound reminds me of the twin 45 mm side draft Webers on my old BMW 2002 when I put short velocity stacks on 'em, just a deeper note. But I digress...

When I was driving back home I noticed a pretty loud high pitch whine at idle and low speeds. I parked in the garage with the engine running, opened the hood and found that the noise seems to be coming from under the air box. In fact, I felt the box and it was vibrating (not loose or anything, checked that), and I could hear the whine change pitch when I grabbed the box in different places.

I put the cover back on, locked all the retaining clips and as each clip was locked, it gradually got quieter, BUT never went completely away. I can still hear it now that I am kinda tuned to the sound.

So what is up? Anyone have a similar experience? Do not think this is valve train noise or anything like that. Not a noise I recognize after 30 years of messing around with a lot of cars.......

 

If it goes away when you grab the box I'd say it's a "harmonic resonance" associated with the box.. Retighten the bolts that mount the box. Then see what it sounds like......

Utah