I have an '87 300E that has brought our excellent mechanic to his knees. The car acts like it is either fuel starved or off timing under 1000 rpm. After we get it over 1000 rpm it runs like a Formula One racer. It has new plugs, wires, rotor, and cap. The fuel distributor has been cleaned. There is a new O2 sensor. We have tried new fuel pumps and a flywheel sensor. There is no engine light or any other warning lights. Where do we go next, the MB Dealer?