What car do you have?
I easily got a 42 on the mway doing a very constant 60 in my valver and at 70 it only went down and hovered around 39-40, normal town use with occasional roar

was about 28-32.
Before that, my normal was btwn 17 and 24. This was due to air leaks, injector seals, dodgy TCI module and general lack of maintainence by previous owners.
There are thin clear vac pipes that go into cloth like braided rubber hoses, check these havent perished as they control the mfa readings.