'85 123 300Turbo Circ Air Safety Valve

[cbcarter]

On my 1985 300D, I have a diaphram that has bone bad in the Circulating Air Safety Valve. This component is only on 84 California, and 85 all USA, and is only breifely mentioned in my MB service books. (page 14.8-050/15 & itme 71 on page 14.8-100/12 of 617.95 Turbo Diesel service Manual)
With the diaphram bad, as soon as RPM gets to about 1000, and vaccuum solenoid to this valve opens, I loose all vaccuum because of the pressure that I get. I have unplugged the electric switch (itme 81 on 14.8-100/12) which causes this to open so that it is never "opened" to vaccuum, and all seems to work well.
This part does not show up at my local MB parts dealer that I use, and they suggest I go to a diesel service shop. I have not been to the MB dealership.
When I undid the 3 bolts holding the cover on the valve, there was a broken blue metal ring/cyclinder that had apparently caused the diaphram to go bad. I have not taken the diaphram out.
Any suggestions on what this does, and if I should repair it, or ???
Thanks