The kicker is I don't know what is upstream. The open line was found next to the battery with no other vacuum line lying around to connect with. I'll keep poking around.

Don't you just love it when a plan comes together!

B52rule

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1960 190D (college car), gone
1995 E300D, 325 k
2019 LEXUS UX 250h (spouse mobile)
2003 Nissan Frontier Crew Cab
2007 Jeep Grand Cherokee Overland 3.0L MB diesel, 185K
1978 GMC Classic Motor Home