NSX Oil Pressure

new to forum, so go ahead and blast me if I misstep...have 91 NSX...rarely driven garage queen...sorry...runs fine though...recently encountered problem with stripped oil pan drain plug...fixed...now, being extra sensitive to engine operation, noticed oil pressure gauge fluctuates...upon starting, needle goes to fifth bar (4 is middle of gauge)...then after engine warms, needle gradually drops...stays high while revved beyond idle...but at idle drops to 2, even 1. Again, rarely driven, but recall that pressure previously remained constant at ~4 or 5 bar position...am I dreaming or is my oil pump heading south for winter?