There are five vac hoses that are hooked to the vac tree coming out of your intake manifold over on the drivers side of the car -on the back side behind the throttle body-remove all of them and replace with new hoses and the rubber mounts that attach them to the vac tree. While your doing that there is a 10mm bolt that hold the vac tree to the intake-take the bolt out and then you can remove the vac tree as well. There is a rubber 0 ring that seals the part to the intake. You can replace it or do what I did that works better-I applied some sensor safe sisicon gasket maker around it and stucker the sucker back on and then put the bolt back in. I'll never get it back out now but it's not going to leak again either.
You need to check all the vac lines over by the hook ups that go back into the cabin-they are over on the passenger side of the car on the fire wall-repalce all of them as well. If you have never done the above, it's high time it was.
Hope that helps
Poolman