This is sort of the inverse of the Lesbian porn question. Same answer, the shit is boring, after the initial shock value.
Ass fucking in general is a turn off for me. The oral and dick stroking is interesting for a few minutes then it gets old like the tit-licking in lesbian porn; the kissing in Gay porn, like the butt fucking is an absolute turn off.
The acting is atrocious and I can't relate to the characters or how they act (frankly they don't even remotely act like any of the Gay guys I have known or met, let alone when they try to pass themselves off as "straight")
To your question the only time I can think of was jerking off watching a cute Ladyboy give a blow job, that's as Gay as me whacking off to Gay porn got, so maybe I was bordering on 89% percent straight that day.