It was an american film, but I don't think it was mainstream. Definitly a porn.

In 1987 or 88, I was in Boston in the Combat Zone, at some gay cinema, and I saw a movie which involved a father and son and some guys breaking into their house and forcing them to have sex with each other, or the son being forced to watch while the burglars fucked the father or some combination therin. I can't remember the title, and have been trying to find it for years. Any one have any clue?