palmsofvictory

I have a 1990 Honda Civic Hatchback with a '95 1.6L DOHC ZC engine swap. Recently it started idling erratically. It revs up to 3000, drops down to 500, then kick back up to 3000, etc... It does this for about 3 minutes until it starts warming up. When it's almost warm, it hits 2000rpm and slowly drops to 1000rpm, and then it's ok.
Any ideas?
A friend and I think it's a vaccuum leak, or the idle control.
Thanks for the help.