I'll cast my vote with Airfoil. After working on these beasts for 30 years as a professional mechanic, I have never seen rock hard seals cause any erratic readings, however, the seals should be replaced to prevent leak down. I believe you have an electric sending unit which has never proven to be as reliable as a mechanical pressure gauge, but hey it's the cheap American way. I'd check the sending unit.

Good luck,
Peter

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