Ok so i'm headed up to college and all of a sudden my car looses power and drops in rpms and the rpms just go up and down. I pulled over and turned the car off. No belts broken wires loose. I go to start it up and it starts up but then backfires and stalls. I just changed the spark plugs with some NGK two step colder plugs for nitrous but I did that 4 or 5 days ago. Anyone know what is going on? BTW I have a 91 prelude SI

 

What mods? Sounds like an ignition problem.