burning icm's, 91 2.3

Truck was running like it had a bad miss. Codes for egr, replaced, crank position sensor, placed, icm replaced, fuel pump replaced, exhaust side coil pack replaced, o2 sensor replaced. All codes are clear, but when driving at high speed, it cuts out, and even dies. If I unplug exhaust side coil pack, it fixes the problem. The only out of spec I see is alternator pushing about 15v, my question is this, could higher than ideal voltage from alternator be fouling the icm?? Or could the pcm be bad also?