I had the exact same impression of Vinny when the show first started. I even liked him then, but now I can't stand him, he's sort of become more extroverted, and a bit of an ass hole. Even Pauly D said "You've changed man", in one of the episodes.
It was the earrings.
Fame definitely got to his head. I still think he's I, probably SP which Se could account for the extraverted seeming traits. He's mostly like that when he's drunk anyway which isn't the best measure.