96LT1TX

I just reinstalled my heads, cam and everything else on the motor w/ a elec water pump, 160deg tstat, and a new opti spark installed. I started it and it fired for about 3 seconds, and after idling high it died and wont restart, I changed some vaccum lines, no help. I did realize there are 2 more vaccum lines I need to put on the intake manifold, and was wondering if that and an o2 sensor that I couldn't find for one of the headers would cause this??
an SES light was on, so tomorrow I will replug in the battery and see if it will restart and then die again.... any advice helps.

thanks again,