Had a similar problem, mine was a bad upper tensioner.

So how would you know if it'* the upper tensioner? I"m able to hit boost.. but then have it dump down to 2-3 PSI only

My boost guage would jump all over at idle occasioally. Thought belt was slipping, had gatorbacks put on, while doing so tech told me my upper tension was poor. He kew nothing about boost problem. Relaced tensioner no more erratic boost guage.