Check your crankshaft reluctor wheel!

I have a 5.7 based stroker in my drag car. It started getting very inconsistent. We took the motor apart and the bolt on reluctor wheel had come loose and you could move it 5-10 degrees! New reluctor wheel will be bolted in AND tack welded! If you plan on going over 6500rpm regularly like I do, I would highly suggest you tack weld your reluctor wheel to the crank when you have it open.

Those kind of things can drive you crazy, trying to find; unless you have a way to capture signals / flight record the events, as they happen; and even then, you may not see anything. I had one of the cam gears work loose (similar to your issue), on a DOHc V-6. Normal driving - no issues. Try to accelerate hard- it threw codes that didn't make sense, including ABS codes. Talk about tail chasing...

See @408 swinger posts on defective casting reluctor wheels and the edge of insanity that it created.