I have read you can "buy" replacement springs, stiffer, to increase oil-pump pressure output.

Where can you buy such replacement springs? I have also read that some people insert washers to accomplish similar results.

This unit was sold as a Hi-Volume pump, and oil- pressure when operated above idle is fine, but at idle the pressure is lower than I'd like to see it (5-psi.)

The motor oil is 5W-30 Mobil One Full Synthetic.

Note: This is NOT the 440 engine in my Charger, as that pump / engine has plenty high oil pressure at all rpm's.