Book, it follows a guy in a dystopian future

Question

I think the guy was a private investigator. He has a sex change girlfriend, takes pills to get different boosts of sorts and has pills to give them a softer let down, I remember triangle and star shaped pills I think? I was thinking the triangle pills were blue.

Most also have a jack in port in their head that lets them gain new info and know things. This might be wrong, but I think he was one who had avoided getting a brain port, but in the course of the book he got one. I do remember that at the end he gets in a fight and plugs a black chip into his port and goes feral. He doesn't remember anything, but they tell him it looks like an animal had killed everyone there, everyone he knew was disgusted with it and left him basically under the power of the manipulator who had gotten him the black chip.

I found out later that this is part of a series of books, not sure how long. I read it 15 years ago or so, sorry if my details are lacking.

Answer 1

The book is When Gravity Fails by George Alec Effinger. The protagonist is Marîd Audran and he is an investigator of sorts.

The sex change girlfriend is called Yasmin:

I left Yasmin a note telling her to lock the door on her way out. Yasmin was one of the few people I trusted alone in my apartment. We always had a good time together, and I think we really cared about each other in some unspoken, fragile way. We were both afraid to push it, to test it, but we both knew it was there. I think it’s because Yasmin hadn’t been born a girl. Maybe spending half of your life one sex and half of your life the other does something to your perceptions. Of course, I knew lots of other sex-changes I couldn’t get along with at all.

The pills are indeed blue triangles:

I held the phone to my ear with one hand and reached for my pill case with the other. I fumbled it open and took out a couple of little blue triangles. They’d wake me up fast.

The module that drives Marîd into a frenzy is called the black daddy:

The black daddy was still torturing me, still burning like acid inside my head. All my screaming, all the infuriated, savage ferocity of my attack, did nothing to lessen my torment. I slashed and clawed and ripped at Hassan’s bloody body.

Much later, I woke up, heavily tranquilized, in the hospital. Eleven days had passed. I learned that I had mangled Hassan until he was no longer alive, and even then I did not stop. I had avenged Nikki and all the others, but I had made every crime of Hassan’s look like the gentlest of children’s games. I had bitten and torn Hassan’s body un til there was barely enough left to identify.