Alternator issues

I recently had the dreaded timing chain
codes on my GMC Acadia. Was idling
horribly and all four timing codes were
on. Decided to do work myself, found
all three timing chains were stretched.
Did the job with the engine in the car.
Put all back together, started her up
and seems to be running beautifly.
Drove her around to test for about 85
miles all was good until suddenly
battery saver mode popped on and
found that alternator was no longer
working. Running completely off
battery. Got home, got her fully
charged up overnight so I could run
some tests and when I started her up
the next day all seemed good again.
Drove around 50 miles worked good
then suddenly quit again. Both times
seemed to be when i had to go full
throttle to get on freeway. Could be a
coincidence but that is when the
voltage dropped initially. No other
alternator problems in past, no other
sign of failure like noise etc. Just
working great then suddenly not at all.
Since I just did the other work to my
car, I wonder if it is related. Does it
simply sound like a failing alternator or
is there some connection I possibly
damaged or something I could have
done wrong? I did not remove the
alternator at all but the wiring harness
did get moved around and maybe dirty
etc. All looks good but I just dont
understand how it either works or
doesn't. In the past a bad alternator
just wouldnt turn on or it had signs of
failing while trying to work. Any ideas?