vaccum advance
 

when its hooked up to full manifold vaccum my idle goes way up and comes down very slow

Need more input here. What year, make model and engine do you have? How many miles on the odo?

A 1980 Malibu 350 about 200. Miles on motor

whats your timing set at without it hooked up?

About 12 advanced

First, I'd set the timing back to 8, is it hard to start?

No starts up right away,but with my cam I need more timing.

When I run the car with the advance not hooked up it's fine,throttles nice and it comes right back to idle

Does the vacuum line run directly from the carburetor to the vacuum advance unit? Back in the 1970's and for some of the 1980's, the vacuum line would be connected to
a small device that would slow down the drop and rise in vacuum, and was an early smog control device, that is why I ask this question.

The cam is not standard, or is built to this engine? At what idle rpm do you have X vacuum? What is the vacuum at say 700 rpm? As oilcan has pointed out, yes the older cars (I have a 70 delta 455 with remninants of smog control) that had a tps that also controlled vacuum advance. This was a small ported attachment. My suggestion is for vacuum advance to set the timing without vacuum, and use a vacuum port from the intake manifold, not from carb, shew, long winded.