Apeks does tune quite stiff out of the box, you could get it alot hotter if you want, but if it breathes fine i'd just leave it like this. The purge works and isn't causing issues as far as we can see?
Agree with you.
I took it to an Apeks service center and was fortunate that the head Apeks service manager was there.
He listened to me, saw my videos and then tried the system.
He even checked IP when I asked. It was centered at 150 PSI.
He said that the Apeks is designed to be a cold-water second stage and inherently does not release as much air as a Scubapro.
To prevent first or second stage from freezing.
In addition to this, the second stage is compact by design. The diaphram and lever are smaller than on my Scubapro and therefore have less leverage on the air-demand system.
Try switching seconds and see if there remains the same delay, as pointed if it works fine that is all that matters but it could e interesting.
Would be interesting to see how a second stage S 620 Ti performs on a first stage Apeks and a vice versa.