Track down a vacuum leak?

[Dave Rifkin]

I recently purchased a 1969 Corvette coupe. Shortly after purchase I took the car to a well knkown Corvette shop in the area to have them tune the car up and give it a once over.
Before taking the car there I noticed that the car idled rather high after warm up; like 1100 rpm's.
When I got the car back it ran better but, I was told the idle is still high. The shop thinks the car has a minor vacuum leak which is preventing them from being able to properly set the idle.

1) Does that sound right to you guys?

2) Is there a easy way to track down a vacuum leak?

BTW: the carb is a Quadrajet if that makes any difference.