Unless you have a pressure tester, there's not much you can do. Low oil pressure either means a blockage at the point where it picks up the oil, a bad oil pump, a bad sending unit, or increased clearance in the crankshaft (and other) bearing journals.

Or, simply a bad gauge...

FYI - an engine flush can be a bad thing, especially if you don't do them routinely. They have a tendancy to dislodge large chunks of nastiness and deposit them all around your engine's oiling system, sometimes blocking up things that ought not be blocked up.

Try removing your sender and checking to make sure enough oil is getting to it to read the correct pressure.

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A.S.E Tech A1,A6,A7,A8 & MVAC 609 + EPA 608

Unless stated otherwise, any question I ask is about my greymarket 1985 380SEL.