glad to see you 'round these parts again MGS!
I've had sex on many psychedelics, but the one that allowed me to have sex for the longest (improved performance not just sensation) was 2c-e and I swear I had sex for at least 6 hours during the plateau/comedown.
craziest combos I've had sex on - (by the way I smoke weed like all the time so THC should be added to all of these as a default lol)
6 hits of LSD, 20mg adderall, a lot of beer (I'm pretty sure it was like 12 over the course of the day), and 20mg valium (the night before) also produced one of the longest sex marathons i've ever been capable of, unfortunately all the beer and valium makes the memory a little fuzzy though.
1 gram of mushroom shake, ~40mg MXE nasal, and some beer and weed was one of the most memorable psychedelic sexy times I ever had. Mainly because as soon as I stepped in the bedroom with my girlfriend the mushrooms hit me all at once, and while I was doing her from behind I started floating up into neon green patterns and having extreme shroomy ego softening.
1 hit of LSD staggered into two half hit doses an hour apart, then 45 mins later a capsule of 80mg MXE oral produced the most psychedelic sexual experience I've ever had. I didn't tell my girlfriend I was on LSD so I felt like I was doing something inherently wrong the whole time. My girlfriend was drunk and being a very generous lover and I kept thinking I was in some strange pleasure purgatory that wasn't supposed to exist in the normal universe. I legitimately thought I was in some other realm because of how unbelievably good it felt and how much I didn't think I deserved to feel so heavenly. Afterwards I ended up telling my girlfriend and she got mad that I didn't tell her from the start, which gave me very bad anxiety so I took 2mg of xanax and went right to sleep.
3 hits of LSD + a forgetful quantity of etizolam had me in one of the most animalistic states I've ever been in. I wasn't thinking in thoughts I was just aware of all the amazing body sensations I was going through like our skin rubbing together or her breathing on my neck.
I definitely love sex on MXE, so 3-meo-PCP would probably be very similar (if not better because it's less incapacitating)
I would say LSD makes sex feel better than any other serotonergic drug, but GHB makes sex feel just a little bit better than LSD.
LSD + GHB would probably be the best sex combo ever IMHO