there's 2 scenes of sex with tao (as far as i know)
one involving tao and scrap in scrap's house and other in the junkyard with tao and a random ratkin. i would help you but i really don't remember how i get the first scene, but the second you need to make Tao your property, go to a place in junkyard with him where's a ratkin stuck, and you will get the choice to have sex with him (this only happens if you libido is at least 40, as another guy answered my comment)