I need help tuning a 2 stager

[tim-]

normally flare connections is what's leaking if something is leaking. it's not that common a brazed joint leaks.

I would check the flare connections. Ofcourse you should strip both stages down and pressuretest it and search for leaks anyway.

I havn't splitted a cpev in part so I havn't seen it i pieces irl. but ofcourse there is a possibility the valve is leaking. But my suggestion would be to chech flare connections first as it's what I would guess is leaking especielly when it's leak slow. those are often hardest to get 100% leakproof. I do prefer expansion valves with brazed connections.

some loctite 542 or something simular would be good to seal flare connections if it's leaking.

regards
Tim