SOLVED!: E53 X5 3.0 sounds like dying banshee on fire when I take my foot of the gas

[IkirisTheX5]

Hi fellow X’ers,

Although been reading and learning from Xoutpost the last couple of years since I adopted my beloved rescue 2002 X5 3.0 (that’s taken me from Texas to NYC to LA and back, and spent several nights at the Salton Sea, in Death Valley and the Badlands having never let me down), this my first official rookie post. So apologies for any gaffs, but I need help, serious HELP!

As of about 90 days, every time I drive the X5 for more than 30 mins straight a higher pitch squealing or whistling begins screeching out of the engine bay everytime I simply release my foot of the gas, and gets louder when I apply the breaks - then - like magic the ear-piercing screech instantly disappears when the truck comes to a full stop or I give it a little bit of gas. It’s so loud it literally sends people begging for change at interjections running off in pain, with ears covered.

Myself and two Indy mechanics I trust and respect have given up on her. So far we’ve changed:

- the valve cover
- the 90° rubber intake elbow boot
- the air filter unit including resonator box
- the DISA valve
- the brake booster
- have performed the smoke test on vacuum lines to no avail
- I sprayed a can of carb cleaner in/around all intake components to detect a breech of some sort - nothing

I don’t know what to do next and I can’t imagine the dealer-stealer can’t help anymore than what I’ve done at this point.

PLEASE PLEASE has anyone ever resolved this in their own vehicle or have any idea what I could check or replace next?

Xoxo