I got my Z up and running. It idles rough. It sounds like its missing. When I increase the rpm's or give it gas. It runs perfectly fine. Anyone have some theories?

What year Z? Does it have carburetors or fuel injection? Has someone done a turbo swap?

Could be a loose or cracked vacuum line or AFM boot. Throttle body might need cleaning also.

I second the vacuum leak theory. At idle the intake manifold is at a high vacuum resulting in significant air entering through the leak, leaning out the mixture. As you open the throttle, vacuum drops and less air enters via the leak, and the mixture richens.

What is the fuel pressure on the rail?

It's a 1978 Z. I think everything is stock. I'll check the fuel pressure later this week.