Is it possible for a alternator to hold voltage while you are driving at a good pace but not hold voltage at idle or at a stop, or would it just shut down any time driving or not.

Yes. The power output of the alternator is proportional to the speed it spins. What you can see is that the electrical load is greater than the power output from the alternator at idle (car is running on the battery.) It'* usually nothing to worry about, so long as the alternator starts recharging the battery when the car is off idle.

If it gets really bad, (like you are hooking the car up to a charger all the time to bring the battery back up) then start looking for the fault. Could be an old battery, regulator, or some bad windings in the alternator. Can also happen if you start messing around with pulley diameters.

well I am still chasing problem with car stalling at stops once in a while, also sometimes a hard start and I never had starting problems.Sometimes it will go 2 days without issue.I changed ICM , COILS , ECM, cleaned IAC , EGR CLEANED AND CHECKED GROUNDS AND HARNESS.It is very intermittant.Alternator checked ok at part source bench test and battery is 3 months new.When it stalls rpms get down to 400 , voltage gauge goes down and it stalls.I still have power as lights are on and it starts right up.Was thinking alt was weak, if not I am thinking crank sensor which I hoped not.I do have 14 .2 V on battery while idling.

Ok, well, I think your are looking at the problem backwards. The low voltage is a symptom of the abnormally low idle speed, not the cause of it. You obviously have enough juice to start the car back up. Now, to figure out why the engine speed is dropping so low. You can completely remove the alternator and still run the car..for about 20 minutes till the battery goes flat. It would be a rare thing if the alternator actually is causing your problem.

Looks like you already hit the most likely easy fixes, I didn't see it in your list, but have you already clean the MAF wire? Though I have to say that the problem you are experiencing with it cutting out intermittantly sounds like an ECM or wiring problem.

I agree.

How old is the fuel filter?

Fuel filter is 6 months.I agree with ECM , icm wiring is possible problem Ive been over it 3 times and changed them out, frustrated.Maf was changed out last year (would prob set code , no ).I was going to look for new ICM harness.
JR -i will check voltage tomorrow