I had this on my first Mercedes, a '91 TE/M103 at about 70,000miles (always maintained meticulously by me). I tried "everything" including a complete new fuel distributor, new ECU, etc., etc. to cure the problem. I also tried many fuel injector cleaners including the common dealer favorites.
The cure came when I ran a single bottle of RedLine Complete Fuel System Cleaner SI-1(I think it's called), cures the bad spray pattern etc. in many of my CIS cars and cured the part-throttle hesitation within the first 1/2 tank-full.
For $10, find a bottle and pour it in the tank, best money you'll ever spend IMO.
Your car will become addicted though, will respond well to the 1oz/10gallon maintenance dose for a while 'till it's cleaned up.
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Gone to the dark side
- Jeff
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