After reading well over 100 private eye mysteries right after 1999, I started in on my own "Mike Angel Dark" series. One of the things I'd noticed is that romance and even semi-explicit sex scenes were not usually part of the sub-genre. I made Mike's conflict over commitment, love, romance and such part of the sub-plot of all the novels. So, yes, I have at least 2 or 3 steamy scenes and much romance as Mike gradually moves toward a lasting commitment with his optimistic, brown-belt, super spark plug love interest, Molly Bennett who became his secretary in book 2. Because he is cursed with a roving eye, Molly wisely tells him "fib if you have to," and that she can wait for commitments, sure in herself that she is what he will want and need long term.
This creates several triangle situations in the novels, and often a great deal of tension, aside from the cases solved and mysteries confronting Mike and his older pervert of a partner, Rick Anthony. So a new sub-genre? Hardboiled mysteries with steamy romance and seduction? Yeah. Let me add, for smartasses.