I posted this at the MBCA forum, i figure it wouldn't hurt to troll here for info/help as well.

This past Xmas, my 1987 2.3-16 effectively eliminated all Xmas money I had received (which wasn't much) and then some to the tune of approx $2000.

Initial symptoms were flat spots in the powerband when accelerating moderately. This occurred in all gears between 2500 and 4500 rpm. As i found out (much to my chagrin) the fuel pumps were on their way out and wreaked havoc with the fuel pump relay. All in all I went through three fuel pump relays and two new fuel pumps.

That was before New Year's. Now my car has started suffering from the same initial symptoms. The engine is unmodded, exhaust is cat-less and car is probably due for a valve adjustment. OVP was replaced a coupe of years ago and the air flow meter was replaced 5 years ago.

It feels like a fuel delivery issue, but I'm not familiar enough with all of the sensors and the intricacies of the system to evaluate why only in a certain rpm range. Before I go back to the dealership and have them re-examine the fuel system, does anyone have any thoughts on what the root cause of the problem may be?

Thanks in advance!
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'94 W124.036 249/040 leder; 8.25x17 EvoIIs
'93 W124.036 199/040 leder; 8.25x17 EvoIIs, up in flames...LITERALLY!
'93 W124.036 481/040 leder; euro delivery; 8.25x17 EvoIIs
'88 R107.048 441/409 leder; Euro lights
'87 W201.034 199/040 leder; Euro lights; EvoII brakes; 8x16 EvoIs - soon: 500E rear brakes
'70 R113.044 050/526; factory alloys; Euro lights