1999 Buick Riviera vacuum line missing

those plugs are available at any auto parts store they come in various sizes. we have no pics of any of the vacuum systems only diagrams an dit doesn'show any going to brake booster. if it's a hose that is supposed to be connected it should bel;ying around on the frame there

No hose laying around. (Bought the car used) Just a piece of hose left on the nipple connector. Here's 2 pics. (Note: what appears to be hose feels more like soft cellular foam-like material.

from the looks of it it looks like the exaust gas solenoid see if it is leaking vacuum and the foam that was around it is probably what it's supposed to be.

Mystery Solved! You were right about the foam. I finally had a mechanic friend call me when he had a Riv come in for service. The missing piece on mine was a foam block on the other. At least I know its not supposed to be sealed in the vacuum system. Still in the process of testing for leaks. Will get my hands on a metered vacuum pump tomorrow. I'll let you know what the outcome is. Thanks.

you shold have 20" of vacuum or around there at idle but normally vacuum leaks are found by ear feel and spraying choe cleaner around inte base o f carb etc fo that. iknow yo have fi but that is how they are found.

First, thanks for all of your help. Everything's coming together.

I found rotten hose connections and now have a solid vacuum (vacuum hand pump and meter) throughout (hoses & modules), with the appropriate sections plugged. However, the S/C bypass valve actuator leaks slowly on the lower hose fitting that is connected to what you named the "exhaust gas solenoid" top fitting (see pic). Vacuum's solid as a rock on the upper fitting that leads to a distribution point on the top of the S/C housing for the brake booster, etc.

Is the actuator bad or going bad because of the leak I described?

it's been a while sincei've worked on that system If it's not setting a code I wouldn't worry about it. you could replace the solenoid if you wanted to but that may be why the foam was there was to let some vacuum leak. thre are two different moldles of the solenoid one can be open and the other can be closed it shold give vacuum to egr valve only above idle like 1500 rpm at least if it is givn gvacuum to the egr at idle then replace the solenoid.