At the shift-point of 1,800 - 2,000 RPM, (NOT under heavy accelleration - just regular run-up) the car has a; WAAA and a possible slight metal vibration/rattling at that RPM when shifting.....not the transmission.

Sounds like air-filter assembly???? OR somethin' loose under the hood, or??????

Naturally, open the driver's window to hear it well.....

Run-up easy through 1,800 RPM.....1st to 2nd, to 3rd. That's where you (if your's are similar) 1,800 to 2,000 IS where you will hear it......

What say the E320 CDI sedan driving gang?

*Tyler - I noticed your CDI is in C or Comfort transmission mode. That's for slick winter surfaces, and or, taking off w/o feeling the transmission shifts - because it starts out in 2nd. I don't see where you would get better mpg using it in stop 'n go driving, FWIW. The little C/S modality selector button is @ 11 o'clock on the flat console near the ashtray.