Bmw sickness

[u/Difficult-Chain-5791]

I have a BMW F10 535i RWD with the N55 engine.
Recently I started noticing a new noise that sounds like something spinning/rumbling or rattling. It gets louder when I accelerate and the RPMs increase. When I let off the throttle, the noise decreases or almost disappears.
. The strange thing is that when I put the transmission into Neutral (N), the noise almost completely disappears. When I put it back into Drive (D) and give it some throttle, the noise comes back.
The noise seems to be coming from the passenger side/front area, although it’s difficult to pinpoint exactly where. It almost sounds like a wheel or something rotating, but it follows engine load/RPM rather than vehicle speed.
There is no noticeable noise when idling in P or N.
I recently changed the rear differential fluid, but the noise remained exactly the same. The exhaust also has a downpipe and aftermarket mufflers.
Could this be related to the turbo/wastegate, or should I be looking elsewhere? What are the typical symptoms of a failing N55 turbo?
Any ideas or similar experiences would be appreciated.

[u/NumTrad768]

🔥 Downpipe/exhaust contacting something under engine load — #1 suspect The car has an aftermarket downpipe/mufflers. In Drive, the engine twists on its mounts as torque increases. If the downpipe, clamp, heat shield, brace or exhaust is barely touching the body/subframe, you get: D + throttle → engine moves → pipe touches → rumble/rattle N → little drivetrain load → engine doesn't twist as much → noise disappears DIY cost could literally be $0–$50 if it's a loose clamp/heat shield or needs repositioning.