As you can see, there's not much sex in the New Testament. We've got the whore of Babylon in Revelation, Paul saying there's no time for sex because Jesus is coming in 1 Corinthians, and Jesus telling us to cut off whatever body part causes us to commit adultery in our hearts in Matthew. But that's about it.
The Sex Index is defined in the usual way (Sexual encounters per 100 verses).
I think we have a winner here. Nothing beats the Song of Solomon for sex.