Doomknight said:
Define pulsating cock?
Whenever I play the game, the cock and testicles does pulsate during an orgasm, so I and the modder (the person who would be willing to do it) who would do this would need to know what you mean by pulsating.
Well, I can't speak for the original poster here. However, as it seems you haven't gotten a response from them for about a week, I'll throw my two cents in. If I were to warrant an educated guess, I'd say think of how certain tentacles in hentai act when they're climaxing(This is a decent example; http://31.media.tumblr.com/42609501fd63bfa9ff9d3373aa7c526f/tumblr_mw4nwgT0SP1rsv6t3o1_250.gif), but apply it to the prostate exclusively.
In other words, while it is true that it does pulsate in the vanilla game, it doesn't exactly look like it's actually pumping anything, shall we say. Now whether or not this is what the O.P. meant, I don't know, but it is the best estimation I have at a detailed description.