i try to change the throttle position on the om617 slowly, because when i do it quickly the engine seems to roar or lunge once or twice before settling at the new level of throttle. it's kind of embarrassing when i have a passenger. the feel gives me the impression of an eccentric weight, out of balance. i can't think of anything that rotates about 1.5hz in the engine, though since it affects engine speed i'm guessing this has to do with the IP. (unfortunately no tach installed yet.) will this mean my rack damper spring is worn out? - other thoughts? cheers!

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'77 240D, 504H, OM617.952, etc.