Joe,
A vacuum chamber would most likely warp or twist your stock. I would guess that the mystery oil's viscosity is too high to just drip out so it would need to be heated. Heating the stock and them placing it in a vacuum chamber will cause all sorts of nasties in regards to the grain structure. Plus you will need to keep the chamber heated to draw out all the old oil. Stay with the above ideas, it may take some time, but it works.
Chris