Don't know if this would help diagnose your issue - but a trick I used to use back in automechanic days for finding a miss/bad spark wire/plug would be to use an inductive pickup timing light. It can tell you if and when you're getting spark, since the inductive pickup only "fires" if there is enough electricity flowing. That would show you if the spark was failing when it was running bad.
Biggest problem is that you also have to pull the trigger on mine. If you have to be moving (under load) for it to happen, you'd have to secure the timing light and strap down the trigger (and the excess lead wires of the TL).
Two roads diverged in a wood, and / I took the one less traveled by, and / now where the hell am I?
'Being an adult is so much better when you forget that you're supposed to be boring' (D.Corsetto, 9/7/12)