90 PSI Oil Pressure.

The seal is not connected to the pressure system; can't see how on earth that would cause any pressure drops....???

Start with a new gauge as a check. Pump relief spring on the Melling HV is 72 psi. If truly high, it is high out of the pump and that can only mean the pressure relief valve is hanging up.

• If the filter was blocked up now, or a remote hose kinked, then there would be LESS pressure at the sensor location because the sensor is downstream from the filter area.
• If the filter or adapter was blocking flow before and dropping pressure, and masking the fact that the relief valve was hung up all along, then you very probably would have seen lower pressures with higher RPM's before.

The relief valve being hung up would indeed be discouraging...... but it is what it is..... Was the pump dropped or tapped hard at any time?