lt1 power

hi i have a 94 z28, and recently finished rebuilding my new motor, i have put a little over 400 miles on it now. Ever since rebuild it runs lean and has always hard to crank over, takes about 3 seconds of cranking before it starts, and while driving it surges all the time. i checked the fuel pressure with the key on it was about 41 psi and idleing was about 38 psi. i took it to the track yesterday to make a test run the car only ran 13.49 @ 100. should be running low 12's. i now have h/c, stall. my car use to run 12.9 @ 106 with bolts ons only. what do you guys think could be wrong with my car???