1988 Plymouth Sundance, Idle problems.

My car has been having trouble keeping a smooth idle. The car will start and then die immediately. If I hold down the gas for a few seconds and let go it will idle smoothly and I can drive it just fine. Sounds like the idle air control motor right? I get an error code confirming this so I took out the iac motor to see what would happen. The car should idle at about 3000 rpm. It doesnt. It gets to about 2000 rpm and idles erratically. After a few seconds it smoothes itself out and goes up to 3000 rpm and then dies. After this I get a code for the map sensor. This seems normal as with such an extreme vacuum leak it should tell me that something is wrong. Car has a new fuel pump and filter. Fuel pressure is fine at 14.5 psi. Compression is 135+ in all 4 cylinders. All 4 plugs are getting spark. I noticed that the brand new spark plugs I put in were covered with carbon (rich mixture?) So I changed the oxygen sensor. Fuel injector seems to be running smoothly as far as I can tell. Any other ideas?