Do you still get the whine when you use the VR mode of the ULF, (not when making and receiving a call)?

It could be that the ULF audio out is picking up some interference from somewhere (the amps at a guess), you could try putting a choke of the ULF audio out on the radio modules telephone input pins.

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Sept 03, M3, Silver Grey. Retro-fits: Modded Mk4 DVD Drive, OEM Bluetooth, VR Control, Rainbow Speaker Upgrade, Sony SOT Amp, HK Sub, CCFL, Intravee II, NightMode.