1990 2dr LS - Very strange problem

Hello I have an 1990 acura integra 1.8 its a two dr and has about 180,000 miles on it. When I got this car it had a problem and didn't run, so I got it for free from my brother. I took the car to a shop and they said that I needed a new alternator and said that it would coast five hundred to do the job. I didn't have the money so I went and bought the part from napa and put it in my self which was fairly easy to do. I also bought a new battery. After that the car ran but it seemed like it was not running at the top of its game, so I put some gas cleaner stuff called heat in the gas tank but the car continued to be a little bit chugy. Then one day I was coming home from work and I was getting up to speed and when I was shifting into fourth I missed the gear and revved the car to about 4000 rpms, then I put the car in gear and kept going and right away it started losing power and the tachometer was freaking out and jumping up and down. The car ran really ruff and the gas peddle didn't really do anything when pressed. Finally I was going so slow I pulled over and the car died. After waiting about five minutes the car started and I drove home (about 15 miles) going fairly slow.

Now the car will do that same thing if it gets up to 3000rpms but I can drive it if I keep the rpms down. What could this be I really could use help here, thanks