If these guys really have been here for 5 years, give or take, I'm having doubts about the AQ link. I get that they might use people who don't immediately have apparent Islamic ties to infiltrate, but sent over here to go to college and do a bunch of stuff and then bombing with two pressure cookers? I would have expected a much bigger event for putting themselves through that kind of trouble.
And CNN reporting that one of them posted on a social networking site that he had no American friends and "I don't understand them." Sounds a lot more like two guys that could just never fit in well.