Oil Pressure in a 3.3L V6

Got a 1992 Plymouth Grand Caravan 3.3L 2WD, 186,000 Miles.

The engine was replaced with a reman unit from surefire, please hold your surefire comments, I already read all the "wonderful" reviews unfortunately after my sister had purchased it and I installed it. Engine replacement was at 182,000 miles, the oil pump was rebuilt with the new engine installation, the engine was filled with 5 quarts of castrol 10w-30 and an orange can fram filer (I wasn't there when she bought it:violent1:). Oil was replaced again with Castrol 10w-30 with a wix filter at 182,500 miles.

I just did an oil change today with Castrol full synthetic 10w-30 and used a wix filter. Now the oil pressure seems low.

When we first put the engine in, oil pressure was at.

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Oil pressure has eventually worked it's way down to

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It would fluctuate in between the above picture and the first one.

Changed the oil today and the oil went to the first picture and then eventually dropped to here on idle:

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As engine rpm increases it will climb to the second picture, at about 3K rpm its fluctuating between the first and second picture.

Any thoughts as to what the hell is going on? Oil is halfway between add and full. Why is it so low on idle?:dontknow::scratch: