I have the same problem in my '88 teg. it revs up then falls down, then up then down...
I just put a compleat new distributor on, and thought it could be the timing but it is not..
It also only does it when warm.
But the engine light just came on, and so I gotta check the code and see what it is.... I do remember this same thing on an '89 CRX hf of my friend's, he didn't fix it ever and used to play it off as if he had tall cams.... (stock HF motor, FYI, the guy was a dork)