Check to see if the noise is coming from the front of the engine on the intake side? The Cam Adjuster may not be set right giving you the trouble when accelerating.

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Bill

1989 300E Smoke
1989 300CE Smoke
1989 190E 2.6 5spd Burgandy
1991 300E w/94 E500 body BLACK
1996 C220 Blue Azure 2000 body
1998 C230 AMG Kitted BLACK