I added the new manifold and the carb from holley and we're getting fuel pressure up to the carb but when we roll it over it doesn't start spraying. Any ideas on what this could be?

spray? carb? the only time you will see a carb "spray" is when you move the throttle (accelerator pump)
if it's a tbi unit then you might have a connection problem

Yeah we're about to check all the connections

double check for any grounds around the manifold, GM likes to ground thing in weird places.

OK thanks! I'll check for that.