Mag leaking like a colander - am I on the right track to fix it?

[ideinit]

My mag setup:
- lv 10 (no shims)
- x-valve
- ULT
- classic rail

Recently when I re-ran the air supply for my mag, from ASA -> valve directly, to ASA -> foregrip -> valve, my mag started leaking down the barrel, and out the back. Re-running the air supply probably have nothing to do with the leak, but it's just the last thing I did before it broke.

After browsing the the tech forums I think I have to do the following:
- replace regular piston (for leak out the back)
- down size lv 10 carrier (for barrel leak)

Also, my mag have always had a leak when the trigger is held, but not when it's released. What par of the ULT do I need to inspect/replace?


The parts are still in shipment, so it'll be a bit before I can test it out, but any suggestions welcomed.


EDIT: Should I just go ahead and replace all o-rings in the valve? I haven't done so in about 6 years...

EDIT: Added x-valve diagram so we can use part # to facilitate discussion



EDIT: added "no shims" as there were many mentions of removing shims

EDIT (03/01): I have done the following:
- completely disassembled the XValve and cleaned all parts
- repack the grease on the spring pack (#23&24)
- replaced reg seat o-rings (#7 & #20), reg piston o-ring (#21), carrier o-ring (#7) because the last one had a cut on it

Now it seems the back valve leak had temporary gone away, but it comes back every now and then if I tweak the velocity setting (regardless of the direction). Also I am still having a barrel leak. So I guess it's time to tune my LV 10.

EDIT (03/01): The initial problem has been fixed by comment #12. But a trigger problem had developed... will start another thread for that specific issue.