Check the TPS! A bad one will cause Motronic to enter a limp home mode the symptoms of which mimic fueling problems very closely.
Corroded electrical connectors at TPS and injectors?
Leaky intake manifolds. If original will almost certainly require replacement. New ones have improved seal.
Ignition,kill switch and ignition key sub sub harness.
for sale: 1968 R 69 S-us original condition