The injection system (D-Jetronic Bosch) uses trigger points in the base of the distributor to time the injector firing. There are 4 sets of contacts and the injectors are fired in pairs in the firing order; cyl 1 and 5 would be first. If I recall the order is 15486372. That makes cyl 4 fire with cylinder 8 (which I know to be true).
If cylinder 8 injector is receiving proper signal then it is unlikely that trigger points are the problem.
Just for info sake; the injectors are fired twenty times by a full throttle activation. If the key is on but engine NOT running one can activated the throttle and listen to each firing (twenty clicks to full throttle). If one turns the engine by hand (socket and ratchet actually on crank bolt), each pair (and each trigger contact set) of injectors can be openned in this fashion.
If one has a scope much can be evaluated using the above technique and by pulling a vacuum on the intake manifold pressure sensor (MAP sensor in modern terms). By watching the changing injector pulse width (due to vacuum changes) the sensor can be evaluated without running the car.
Bosch Master, ASE Master, L1
33 years MB technician