This is a fuel injection car right? (I don't think they used carbs much in the US 'cos of emissions)
If it is, you have the air bleed screw on the side of the throttle housing, the idea of which (I think) is to allow a small amound of air past with the throttle butterfly closed. Then you also have the throttle stop rest, which you can adjust so that the valve itself doesn't fully close.
A good way to test if your vacuum system really is free of leaks would be to screw the the air bleed all the way in and the stop rest all the way out, so the throttle butterfly is completely closed and no air can get past. If you do this with the engine running this should cause the engine to stall, if it doesn't then you know that air is still getting into the system somewhere (i.e. you still have a vaccum leak)
On the other hand if all is well, you should be able to adjust the idle speed with these controls. Its easy enough to do, although but my own car is still struggling with idle during warm-up.