Engine cutout/sputter above 4300 RPM

Engine cutout/sputter above 4300 RPM
All of a sudden my 220SEb cabriolet engine has gone from running like like a fine timepiece to missing/sputtering/cutting out whenever I am accelerating hard and after the RPM reaches 4300. It runs fine above 4300 if I am not accelerating. If I am cruising smoothly above 4300-5300 and punch the throttle, the problem will surface. It almost sounds like it starving and not getting enough fuel or air. I thought it might be a faulty advance but why would it run smoothly when not accelerating above 4300 if that was the case? Changing the fuel filter attached to the engine was no help and inspection of the old filter revealed it was in good condition. Is there an internal filter in the tank? I am assuming that the fuel pressure is ok if it can provide fuel to run at 5300 RPM. Any suggestions on what the problem could be? Thanks, Gregg