[SF335]

I just did a number of mods on my car (2011 N55 335i) and the car has developed a very strange noise immediately afterwards that I cannot identify.

Here is a link to a recording of the noise:

The mods performed were:
- UUC evo3 SSK with DSSR
- UUC poly transmission mounts
- Turner poly engine mounts
- flex disc (replaced with aluminum disc with rubber bushings)
- replaced all shifter carrier bushings.

The noise only happens when the car is moving (never at idle). However, it does not happen until I am going about 40 mph and once it starts it will go on but will occasionally go off. Once I am going over 60 mph the noise is consistent. when I slow to below about 40 it goes away completely. It doesn't change or get quieter and louder with engine RPM or car's speed. Once it starts it's pretty much consistent in volume and tone. I don't feel any vibrations and the car feels great after the mods aside from this.

This is driving me absolutely crazy and I can't figure it out - would be very grateful for some advice and hopefully someone has come across this issue before.

Many thanks for your help.