TE/TC Leakdown pressure test - what should I see?

Hi all - I recently pulled the motor on my '15 TE300 to do the rings (it's at 100 hours and compression test shows 130psi). I thought I'd make a leadown tester while I was at it, so I got a freeze plug for the exhaust port and put together a PVC fitting with a low pressure gauge and a schrader valve that I can pump it up with.

I tested the PVC setup for leaks and there are none. I also put soapy water around the exhaust port and see no bubbles, so the freeze plug is doing its job.

When I put 6psi into the intake port, I see that I'm losing pressure at about 1psi every 20 seconds. That doesn't seem like a lot, but it's my first rodeo.

Any idea what I should be seeing on this particular motor?

Quick update: I found that the air is leaking out of the power valve. I took the PV cover off, disconnected the connecting rod and pumped up the cylinder. I can hear light hissing/burbling from the PV. When I actuate it by hand, I can sometimes find positions where it stops leaking entirely (hissing stops and pressure gauge stops dropping). But then I'll move it again and the hissing resumes and I lose 1psi every 20-30 seconds.

Is this normal? I'd like to not have to pull the PV assembly apart, but I certainly will if I should.