Cold Start problem

[Jeff Lemon]

87 911, just completed a top end rebuild, car idles smooth, no smoke, starts warm, BUT when the car is cold, it will start, run for a second, and die. You have to start it foot off the gas, then get your foot down quickly, to maintain an idle for a few minutes, then it runs great. Local 911 guru says it may just be that the new cylinder/liner combo is very tight, and it will loosen up (only 30 miles so far). He says if its idling and running ok all the rest of the time, the IAT and head temp sensors should be ok. Any thoughts ? This didn't happen before the rebuild, repl O2 sensor, head temp sensor, and ref sensor as all their wires were showing wear. Also replaced 2nd throttle return spring, it only had 1 when I took it apart
Thanks, Jeff Lemon 87 911, 88 535 is, 83 633, 80 TR7, 67 MG Midget, 60 Triumph TR3