15 psi @ idle is just about ok much lower and I would be getting concerned
What concerns me more is the oil pressure above 3000 rpm, much below 40 psi and you run the risk of damage to the big end bearing on boost

Have had lots of fun and games with different oil pumps over the years from defiant manufactures, company’s. To cut a long story short the only pump to use is the original Ford one.

Question, did you have good oil pressure when you first fitted the new pump?

Cheers

Steve