Mildly modified 318 PCV valve selection

1983 318
Hydraulic cam
214/224, 444/466 105 ICL cam
Holley street dominator intake
Holley 390 cfm vac secondary 4 bbl

Breather in driver side valve cover

Oil cap/pcv valve in passenger side valve cover.

Oil cap and pcv currently in the car are left over ford parts from a previous build.

Seems to work well. But……

When I pull out the pcv valve and plug it with my finger the idle drops 300-500 rpm I’d guess.

I know a pcv valve is a controlled vacuum leak, but how much is desired or wanted?

What is a good starting point for choosing a pcv valve?

Idle vacuum in gear is 10 hg

Idle vacuum in park is 15 hg

Thanks. Eric L