I have a 82-280slGray market) mercedes--110 engine--fuel injected.It has been in storage about two years.After starting it---it hesitates bbadly when you rev the engine.I have drained the fuel,replaced the fuel pump(electric) and fuel filter.Still no improvement.Afterleting it run for about 15 min----the problem cleared up.Then,after siting for several hours---the same problem developed.I have checkked the timing--its ok.Sure coiuld use some suggestions.: