guage is nothing but a vacuum guage, so if it is buried that means low vacuum. so this could support the idea that you have a vacuum leak. i suggest checking all the soft connecting parts in the vacuum system. these often work loose with age. if you find loose fittings you can temporarily seal. perhaps but best to replace them. i have seen people check for vacuum leaks by spraying either on each connection with the engine running. if it speeds up you found the leak.

happy hunting

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.