While replacing my heater bypass valve recently I noticed that the vacuum lines were in bad shape and found that the one going from the throttle body to the solenoid on the firewall had come off the solenoid completely.
So I picked up 10 ft of silicone and replaced the old lines.
Here are the old crappy ones:
http://www.saabphotos.com/gallery/al...b_pics_015.jpg
Old vs new:
http://www.saabphotos.com/gallery/al...b_pics_017.jpg
The old rubber lines were very brittle and loose at the ends especially the ones at the top of the engine where it is very hot. The new silicone lines look indestructible. Now the car is idling better and boosting is much improved. If you have an older car you should check these lines.