I had an old 89 190E 2.6 with the same problem to a tee. I would drive down the street....and when accelerating, the check engine light would blink on and off, and when lit, the car ran like crap, no power. I assumed it was my O2 sensor, but my mechanic verified it was working fine. Just for fun, I had a spare computer that was out of a 86 300E. I popped it in, the car ran PERFECT ever since. the light never came back on, it idled right, and accelerated fine.
To this day I dont know if the old computer was bad or what, but I didnt complain because it fixed the problem. I know the computers rarely go bad.
Best of luck.
93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K