I have the same exact problem with my 94 EX. After driving it, and sitting in park, the rpms will go from 1k to about 3k. I sat in the car for a minute or so just watching the rpms do this, and there wasn't any sign it was going to stop.

I'm pretty sure it's a vaccum hose, but not sure where. Also, just replaced the stock intake yesterday, BUT, this was happening before the intake was replaced. I tried to connect the vaccum hoses on the intake to the best of my memory. Anyone know which vaccum hose it could be?