Maybe you have excess carbon build up. Try an italian tune-up. Seeing as you revved the engine to 3000 in neutral, try doing that in gear, and see how it works out.
Other than that... there are MANY other possibilities. Among the simplest though are the Italian tune up and try getting a bottle of TECHRON and running that through a tank of gas.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)