Megasquirt Voltage Spike, any thoughts? Options

[yarin]

I datalogged a few runs and found the issue to my random ignition hitch. Previously I thought the tach signal was dropping out, but you certainly cant argue with this data...

My MSII is grounded to one of the tranny bolts. The tranny groud strap was just changed and cleaned up. +12V is connected to the battery cutoff switch (I think where one of the terminals where the alternator plugs in, i'll double check). Is this OK?

A voltage spike (both up and down) causes Pulse Width to max out, maxing out injector duty cycle, resulting in a quick cough. This occurs once in a while, sometimes every 30 seconds, sometimes not for a few minutes. Voltage never spikes at idle, only when driving at mid rpm.

Could it be a bad connection? (then i would assume the spike would be unidirectional).
Bad voltage regulator on alternator? The battery charges fine, normal operating voltage is ok.

These are about 1/10th sec samples from datalogging:

13.4 13.5 13.3 13.3 21.5 13.9 13.5 13.5 13.3

13.9 13.6 18.6 14.8 13.9 13.9 13.7 14 14 13.7 13.5 8 13.2 13.5

Any thoughts? Where my MS experts at?

Thanks