Well.. premium gas in TX is 93, I've never seen a station selling 90 octane? And octane booster doesn't really do anything at all, so I would not suspect that's a problem.
Squeaking could be a lot of things, usually belts. I've also hears IWGs squeak (not squeal). It's hard to say without knowing what the "squeak" really sounds like.
Usually a blown turbo will make your exhaust smoke like crazy.