Andy, The bolt it's self doesn't get into the vacuum area, but if it isn't cinched up good and the gasket tight, then yes you will have a vacuum leak. You might also check to make sure the spacer ring and the o ring on the W ( air Horns ) going into the throttle body are good and tight. John http://www.specialtauto.com/ << oday i was tinkering with my car and i noticed something odd. you know that plate that sits on the W-pipe on the intake manifold? there are two bolts that hold it down to the manifold with a paper gasket between them. one on of the bolts there is a wire harness clip holding the engine wiring. anyway, i noticed that i was missing a bolt in it, probably from this winter when i put my new waterpump in. i have some extra hardware around so i put a bolt and washer in it, and started the car. it seems to run a little smoother, or maybe it's just my imagination. would this plate being loose or missing a bolt cause a vacuum leak? i don't remember what is under the plate from this winter. perhaps this is another place where people should look when they have a rough idle.... >>