my 1995 960 runs poorly at idle, but its usually fine otherwise. i think it may be a vacuum problem, because the power breaks barely work, and the controls for the heater vents arnt working properly. i'd like to know where to look for the problem (maybe some common failure points in that system)

Try to see what color/construction your intake manifold gasket is.

If it is redish/orange and looks like a regular gasket it needs to be replaced. Sooner or later they all fail. Usually by the #1 intake port on the bottom corner.

If it is greenish/aluminum it has already been replaced and you should check for leaks elsewhere.

I don't think the A/C controls can leak enough to cause engine problems. More than likely you have bad vacuum motors also. Check the FAQs for those procedures. I can e-mail you the factory procedure if you can't find it in the FAQs.
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'96 965, 16' wheels, Michelin Pilot Sports, rear 18mm bar + Koni, 201 HP cams, 129K. Put 200K on '85 745 TD.

Start by replacing the rubber ends on your vacuum lines.along with that replace the long hard plastic line that goes over the front of your engine to the air pump valve. There is a vacuum block on the back side of your intake manifold. Replace all the vacuum ends there as well, replace the larger rubber line that goes up and too the right on the fire wall as well. While your into this vacuum block, there is a 10mm bolt that holds it to the intake. Remove the bolt and take the vacuum block out of the intake,replace the flat O ring on the back with a #30 o ring from lowes hardware.
Next clean the Idle control valve and throttle body as well(check the faqs), after you have done all the above and you still don't have things in order then you should look towards the intake gasket-intake gaskets were upgraded later,your model of 960 seems to have a few problems with them for some reason.
Hope that helps
Poolman