These swings in performance are tied to the AC.I always admire the way that vague symptoms in a nine line post (sounds "wonderful" versus "collection of items purchased at toys are us") can be diagnosed by others with such unquestioning certitude even though they haven't seen, much less heard, the system themselves.
It would like phoning a doctor who has never seen you, complaining of generic symptoms, and getting a precise diagnosis.
Power line issues can cause problems but it is hardly the only cause. Several avenues of investigation have been suggested to the OP. I hope he finds one - or a combination of them - helps with his problem.