OK I finally found it in the Hanes manual, it says its a vacuum switching valve for pulse air injection, something to do with emission controls. The little cyliner I broke off doesn't seem to do anything, so I cut it open. Inside was the tiniest little filter I've ever seen! By the looks of it, I'd say the black plastic is just a splash guard and its simply an air filter. The verdict is I'm leavin' it broken, and I'm off to the pub <img src="/forums/images/graemlins/cheers.gif" alt="" />