GT2s aren't supercharged. Only the 2007 GTs were supercharged, and only because they dropped the GTP name. Pontiac is readying to axe the GP altogether in 2008-9ish to make way for the G8.
The offset is something like +35mm. Anything from 30ish to 40ish mm offset should be fine.
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Originally posted by HercMan:
Sounds like corrosion has had it's way with your nuts.