@M1nd64m3, while I think you may not have targeted the right vacuum source, for you and others on this thread, here is some info on the "missing" BOVs for Explorer STs.
https://www.explorerst.org/threads/2021-st-bov.2576/post-33735
https://www.explorerst.org/threads/2021-st-bov.2576/post-41797