Huh?
I know "vig," but never've heard of PITA(except the bread). 'Splain, por favor.
PITA is, as Lon explained on p1, "pain in the arse" (or "ass", west of Ireland). Someone saying "pain in the arse" is trying to be rude to or about someone/thing. Reducing it to a set of initials takes away the rudeness. So it's a euphemism. I don't usually do euphemism. I'm much more likely to call it a fucking shovel. Which is why it didn't immediately occur to me that PITA meant "pain in the arse". See?
MG
Ooooooh.
I just thought, PITA being a bread, and bread being slang for money, hence the vig is the bread/money. PainInTheAss is most likely though.