Intermittent ignition failure: ideas?? on '91 911 turbo

[MarkRobinson]

I thought this was fuel delivery: clogged fuel filter or pre-filter in the tank, was not it. I checked & replace cap/rotor, only to find that the distributor shaft had 3/16" axial play in it (Could be it).

Crap, swapped on a '94 3.6t distributor: had to re-layout the wires as the distributor & cap are rotated 90 degrees from a 3.3 turbo: wtf did they do that??

Anyway, runs, but my intermittent problem exists! Ultra week/failing ignition & lots of louder (than normal popping) in the exhaust on decelleration. I'll have to check the coil, ignitors, crank trigger (oil on it???): anyone have other ideas??

when the issue presents, it's not just one cylinder: it's more like 1,2, or 3 at a time as the car barely runs, barely accelerates, idles at ~400rpm, stumbles, then clears right up.. does it hot, cold, idle, cruising, uphill, downhill, etc: there's no specific time it does.

I'm looking for ideas...