Electrical Problem

92 Grand AM v6 3.3L....The car starts and then runs for a few minutes and cuts out. It doesn't chug like it's losing fuel it just cuts out. This tells me that it's electrical. I got the alternator tested at autozone and it said it was putting out 1.1AMPs PEAK to the battery so, since it was still under warranty i had them order me a new one (duralast gold 105amp). I go in earlier today to pick it up and take in the old alternator and they test it by itself on their machine and it PASSES with a peak output of 102amps. Becuase of this they won't give me the new one that I had them order for me! My question is - if the alternator tested bad while still installed in the car and it tests good out of the car by itself what could be causing the battery to not be receiving a high enough charge from the alternator?

Sounds like either a bad ground or a bad ecm. The alternators on the 92 and up grand am's are controlled by the ecm, check the connector at the alternator make sure there are no broken wires. Also check all your accessories ie defroster, ac, headlights etc make sure nothing is drawing power. If you have a huge amp in your car that could cause enough of a draw on the electrical system to shut the car down and to cause the alternator to only show 1 amp into the battery.