The black car I've been working on is developing a weird problem. When I rev it up to 2500RPM it starts bouncing between 2500 to 2200. It's kind of like when you hit the speed limiter in 4th or 5th gear. But it still revs higher. It doesn't have any trouble getting past 2500, but I'm just wondering why it's doing it. Could it be bad gapping on the spark plugs? btw, it's an 89 single cam.