I believe it is an episode toward the end of Season 2, though am uncertain as to which one exactly; Richie does Janice doggy-style and holds a gun to her head, before abruptly stopping to Janice's words: "It should be you," [implying that Richie should clip Tony]. Hence Janice's telling Carmela later in the season that she would like to see a gumar that lets Richie hold a gun to her head during sex.
Personally, I find scenes like this very humourous, the way the camera just cuts to a scene in which the two most unlikely participants are going at it doggy-style. And the one-liners including the coarse swear words are sometimes the funniest things in the show: take Junior's frequent deliverance of the C word, for instance!
Take away the swearing, the sex scenes and the violence and what you have is a show without any humour, realism or enjoyable scenes.
Mick