1980 450 SL Injection

I have a 1980 450 SL that had been sitting for 7 years. Since I have started to resore it I have drained and cleaned the gas tank. Put new injectors, wires, cap, rotor, fuel pump and filter in the car. It still doen't run correctly as it doesn't have enough power and it seems to miss or flutter. Compression is good and it also has new plugs. To make it run even reasonably well I must advance the timing around 30 degrees. It starts well just doesn't run well. Any Ideas?