Was the Nitrogen bottle ever hooked up to the manifold gauges? Nitrogen max pressure is around 2000 psi and if you're not careful with the regulator, you could have damaged the gauges by exceeding its pressure.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked