We sometimes watch porn during foreplay, but visual blowjobs turn off my GF... gagging isn't her thing... and it somewhat turns me off as well; girls chocking on dicks isn't really a turn on. I know, not all movies are like that, but it seems those that I get on TV are like that.
However, we purchased a sex DVD/game, where they order you what to do with your partner, it really turns on my partner.
We don't watch that much porn though