what mods have been done to the engine?

I have a 91 CRX Si that does the exact same thing when it gets close to operating temp. The engine idles fine when warming up (cold to 3/4 of the way to operating temp) and once it reaches operating temp. The Engine runs great while driving.
-the original engine never had any idling problems (I replaced it with a ZC because it had over 206k and was burning oil.)
-the guy I bought the rebuilt ZC from had the head done (5-axis valve seat grinding and shaved .030" off the head to increase the compression)
-I'm not sure if that slight increase in engine compression didn't throw off the MAP sensor reading just enough to cause my idle problem

I'm still searching for a fix for my idle problem too.

take care,
ChrisS