Some guys have all the luck! There are some small vaccuum hoses in there, also a horizontal vaccuum accumulator. Looks like a series of plastic balls. I guess that a series of spheres is less prone to collapse than a simple tank! But why should the system hold vaccuum at all if you have the kind of leak that makes the motor run funny?

If you take the hard plastic side panels off you may be able to figure out what is going on.

Good luck...I was in there last weekend-changed out the blower motor, and my hands look like I tried to drag a wild cat through a barbed-wire fence.