If I recall correctly, when I disconnected my cold start injector to test something and forgot to plug it back in, my motor wouldn't fire up cold. Maybe make sure the cold start injector is plugged in and working. Another possiblity would be the cold start injector working too well and flooding the engine.

Another possiblity is a really weak coil not producing enough spark.

Of course any major leak in the intake system like the intake hose not fully installed and sealed will cause a problem, but so will if you have the oil cap or PCV valve remove or any vacuum lines disconnected.

These are just some things I would check if the other suggestions don't pan out. My shots in the dark. Good luck.