Im pretty sure this is the 2-way valve that you changed already, but here it is anyway. I just fixed a '94 LS with that problem. I installed a used canister from ebay and a new Purge Solenoid that I bought from this website.

http://catalog.autohausaz.com/autohausaz/detailw.jsp?sid=pmadzx45qewv3g55ibai5efd&partner=a utohausaz&year=2000&make=AC&model=INT-GSR3-001&category=B2024∂=Vacuum%20Valve