What fuel injection system are you running? 78 Monte didn't have one, and S10's didn't have 350 V8s...more info needed as to what ECM is being used, etc.

Kpi? Inches of mercury? If that 14 is inches, that don't sound too low.

Lopey idle? Hmm, no vac line off, hooked up wrong, leaky vac brake booster?
Sure timing is on? firing order is right?

Is cam set up right (timed right?) Are the valves all set up right and even with eathother (none too tight or to loose?)

re-check the basics!!