I'll take a lot of grief for this, but I've rebuilt a couple of Pressure Sensors.From all I know, what Cameron has said about these thinks being carefully factory calibrated is true, But jeez, these cars are eons old and there's a lot that's out of calibration.

To repair, carefully disassemble the thing (early ones have 4 screws, later ones have rivets.) Take care to note the position of the bellows (copper colored thing), although I don't think it really matters. Then turn your attention to the front (smaller) section and remove the diaphragm retaining ring. First one I repaired (20 years ago) I used a Saran Wrap doughnut glued to the diaphragm's external face with Pliobond adhesive. It worked fine. Latter redid it with 35mm shutter curtain material (I was studying camera repair at the time).

I recently purchased one, as a spare, on eBay. Of course, when I got it, it would not maintain vacuum.So I dug out the old shutter curtain material and bought some new Pliobond at the hardware store and fixed it similarly. During a subsequent session of troubleshooting by swapping out components, I had occasion to use it for several days. No discernible difference between that one and my good one. So go ahead, find some thin, flexible material and some spray adhesive and have at it. You have nothing to loose and you may just be pleasantly surprised.