I have 300E 3.0L but I also have acceleration lag. It eventually starts accelerating good after like 3 seconds when it reaches 3000rpm. I dont think its normal and from what ive read on this forum it must be vacuum leak. I might be wrong. Im thinking to look for leak around Idle air valve hoses but it requires to remove a lot of things off the engine. Im NYC its kinda cold out to do it. Once itll be warm Ill change hoses and couplers. It seems to change RPM when I spray carb cleaner around hoses so I assume vacuum leak sucks carb cleaner in intake manifold and increasing RPM. Like I said I might be wrong. I had 420sel before. It had same problem (acceleration lag) but I never went changing any hoses because the car wasnt in good shape to invest into. I hope my thoughts help in some way. Good luck.

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1999 ML430 Silver 135k ml
Smoked LED taillights, Alpine in-dash DVD player, 12" sub, Pioneer components, 2 amps, 4200k HIDs, ML55 headlights, 20" rims, mirror LED blinkers

SOLD. 1996 E320 145k ml. Burgundy

SOLD but miss it everyday 1992 500sel Black
Chime buzzer mod,Alpine CD/MP3 player with stock amp,Euro headlights,S600 grill,20" rims, BEST CAR EVER!

SOLD. 1990 300E White
187k ml,smoked tails,Euro headlights,17rims,Intake,12" sub in first aid kit,alarm/autostart,buzzer mod