I just finished watching the game on TIVO, and I am glad I waited for the outcome before watching it. Even knowing that the pats lost, I still had a couple of episodes of screaming at the TV.
The first G-Men drive, Harrison CLEARLY lowers his head to drive the top of his helmet into the ribs of the receiver. Unfortunately for him, his actions took Gay out of the game with an arm injury. Of course there was no flag. That's a legal tackle for cheatriots. They used this tackling technique all through the game, and was never flagged for it.
Next comes their first TD drive. Faulk (IIRC) is tripped up and hits the turf a yard short, but slide another yard and a half. They spot the ball right at the first down marker, and it becomes 1st and goal. The PI in the endzone that put them in position to score was legitimate, but wouldn't have happend if they had already kicked a FG 4 plays earlier.
And as the title suggests. When did instant replay become a tool for calling a penalty? When it was first re-instituted, it clearly said that it could not be used to call, or negate, a penalty. So how was the red flag used to call the twelth man penalty? Fortunately for all fans of football, and the G-Men, the pats fell on their sword on that drive. :)