1992 Dodge Daytona Engine won't run at idle

Engine Performance problem
1992 Dodge Daytona 4 cyl Front Wheel Drive Automatic

I've just put a rebuilt engine in (2.5L non-turbo) and the car won't idle. The timing is good to the best of my knowledge (12 degrees), changed idle control valve, O2 sensor, map sensor checks out ok, coolant temp sensor checks out ok, battery is good, new coil, wires and plugs, compression is 130 plus or minus 5 pounds on all cylinders, vacuum is about 18 inches. Starts and runs ok untill it starts to warm up then it bucks a bit and stalls. Will run if I keep rpms at 2000 or above. Will run down to about 1500, but acts up. Oh yeah, no codes except for memory loss (12) from disconnecting battery neg to reset the computer. I've checked for vacuum leaks, but can't find any. I dropped the exhuast, but it made no difference. Also, before I changed the engine the old engine was running ok, but worn out (210,000miles). If I have to remove the intake it will mean pulling the engine because not enough room for torque wrench on re-install, so I'm try to get around that. I've also checked voltages and grounds from the computer and they appear to be good. I'm out of ideas.