I had a whole-house plumbing gurgle whenever any fixture was used. I went up on the roof and removed the 2 rubber caps that had been installed on the PVC vent pipes. Fixtures flush great and no gurgles! Then I noticed a foul smell, and my basement stinks of sewer gas! There are no fixtures down there... The odor may be coming from abandoned sewer lines outside the basement window. (though I have filled these with spray-foam) Would opening up the roof vent cause some sort of vacuum? I hope the stink goes away, it's worse than the gurgle!