I have a 1987 MC LS I'm cleaning up, and today I was going over the engine replacing a bunch of vacuum lines that were horrible cracked, some completely torn open. I figured I was having some vacuum issues when I noticed some weird things like no matter how hard I mashed on the gas pedal, it rarely, if ever, kicked into the passing gear. Not to mention the really rough idling and lack of response from the accelerator. So I replaced a bunch of lines and now the passing gear seems to be kicking in pretty much as it should, and the idle seems to be smoother. Then I noticed that big rubber diaphramed thing on the drivers side inner fender. It has a cable running from the diaphram to the throttle linkage. When I push in the diaphram, it weezes and whistles like it has a leak, but I don't see any tears or holes. My question is what is that diaphram, and does it sound like it's busted? I was thinking it had something to do with the cruise control that my car has, but that doesn't seem to be working.
