Okay, so I'm looking for a Wincest story called (I think) A Little Fetish. It was on Sinful Desire.org, but has now been removed.

It was set after the episode Asylum and starts with Dean and Sam in the Impala, driving away from the Asylum. Sam keeps apologizing to Dean for shooting him and Dean eventually gets pissed off and pulls the car over. They get out off the car and start arguing but it ends up with Dean getting Sam off with his hands and his gun.

If any of you know where I could find this fic, I'd be seriously grateful. :)

FOUND! Link in comments.