2018 Audi S5 (B9) - Metallic Rattle/Zing Sound on Acceleration and Gear Shifts (130k km)

Hi everyone,

I’m seeking some advice regarding a subtle but annoying metallic rattle/vibration on my 2018 Audi S5 (B9) with 130,000 km (approx. 80k miles).

The Symptoms:
- Stationary (Park/Neutral): The car is perfectly quiet. Revving the engine in "P" does NOT produce the sound.
- Under Load (Drive): The rattle appears for 1-2 seconds specifically when I first tip into the throttle or when moving from a standstill.
-Gear Shifts: The sound reappears briefly during upshifts (1st through 6th). Interestingly, the "tone" or pitch of the rattle changes slightly depending on the gear/RPM.
- Consistency: It's not a constant sound; it’s a brief "zing" or metallic vibration that disappears once the RPMs stabilize or when I lift off the gas.

What I’ve Checked So Far:
- It doesn't seem like the typical "Wastegate Rattle" because it doesn't happen on deceleration/overrun.
- The sound is most prominent during the momentary torque-flex of the engine when shifting or initial acceleration.
- Since it only happens in "D" and during shifts, I suspect it's related to engine/transmission movement or exhaust resonance.

Given the mileage (130k km), could this be the exhaust flex pipes failing internally, or perhaps a heat shield resonance? Has anyone experienced something similar where the sound is gear-dependent and only happens under load?

Any input or TSB references would be greatly appreciated!