I am going to suggest something different.
You say the serpentine belt feels tight. V-belts can slip though they feel tight, if they are worn out, but when a serpentine belt is tight, it grips, regardless of age, unless it is really crusty and hard on the surface.
I suspect that you are loosing alternator field signal under acceleration due to a loose connection or a chaffed wire. That causes the alternator to ‘free wheel’ while you are accelerating, and then you hear the chirp when the alternator takes its load up suddenly at high RPM.
I think that your alternator has an integral voltage regulator, so if you don’t see any chaffed or loose wires around it, I suspect that the diagnostic procedure for this hard-to-reproduce-in-the-shop problem will consist of trying a different alternator.