C5 Z06 Charging Dilemma

Seeking some insight here.

Car:
2002 Corvette Z06
New Battery
Stock with intake, exhaust, tune (by unknown tuner)
Factory alternator from Valeo, tested by parts store, Passed
No corrosion on battery terminals or battery grounds.
No corrosion on PCM terminals or Alternator terminals

Complaint:
Charging system operates intermittently. Sometimes the car runs on just the battery, sometimes the charging operation is normal. I have not been able to identify a pattern related to the complaint.
No DTC's
"Charging system fault" display present during low voltage

Attempted Diagnosis:
I have followed the pinpoint test located here: http://www.gearchatter.com/viewtopic10125.php

The result of the test concluded PCM failure. I do not firmly believe this simply because the problem is intermittent.

The car was sent to the dealer to get reprogrammed, problem persist.

I have completed continuity test for S F L B terminals, passed.

L terminal inactive while car running regardless of charging condition.

F terminal approx 15% during failure, approx 75% during normal operation

I have tested F L for short to ground and short to power, passed.

Installed a Bosch 140A, tested good on the bench, failed in the car. Stock alternator tested good on the bench, intermittent failure in the car.

I do not know the amperage of the factory alternator, I suspect it to be 110A.
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Dilemma:
Replace the PCM or Bebuild the stock Alternator?

The factory alternator could be failing intermittently and coincidentally passed on bench test.

The bosch alternator could trigger a system fault if the amps do not match original. Original amps unknown.

I hate throwing parts at vehicles, I do not want to waste the time or money of my customer. Any thoughts?