He may have meant to say "Bypass Restrictor in switch-over valve"

Vacuum restrictors, (I just bought one yesterday cost $3.00) are basically in-line little plastic tubes that hook-up into a rubber vacuum line. They are smaller in diameter than the original line. This effectively reduces the overall dimension of that line, and consequently decreases the available vacuum. Some of these restrictors also have a little filter inside.

I assume that yours was either partially or totally plugged, and that he did not have another one in stock, or that he removed it because he needed to increase the amount of vacuum in that line for some reason.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]