I might be wrong but I don't think the Bruins were ever behind in one single Pens game. I think the Pens were at best tied in these games but mostly looking up at the Bruins.
Also even when the Bruins were outscoring the Pens big early in the series, early in games the flow of play was favoring the Pens. But with the possible exception of Game 3, that never went on for more than a period. From the second period on these games were played the way the Bruins like to play hockey. Without question the worst decision the Pens made was to try to prove that they were as tough as the Bruins. That was a complete waste of time and effort.
As it turns out, the Pens needed every minute of offensive pressure they could get and even then, it never looked like they had an answer for the Bruins defense, especially since even if they beat the defense, they were stuck dealing with Tuuka. I don't think the Pens saw that kind of performance coming from Tuuka.