Glad you got it going, in the first post though you told us the timing was correct.
Kidding aside generally you don't look at these Vortecs in terms of how the timing is set; you're looking at the cam retard angle which is something not all scanners can read and you sure as heck aren't setting it with a timing light.
But regardless of Vortec, TBI, old skewl, whatever - timing should be set with the engine at normal operating temperature. So yeah, if the previous shop that set it didn't warm it up...shame on them.
The up side is that if it had any significant miles on it you'd want those injectors and new regulator in there anyway, as well as a new pump, filter, and tune-up parts too. So there's a big chunk of the money you spent, well-spent, regardless.
P1345 pretty much always comes down to two things. Distributor not adjusted properly because it was removed for one reason or another (lower intake gaskets, distributor replacement, etc.) or the distributor is worn to shit which is pretty common once these hit about 150K or so.