How do you....

[Skyblazer]

....remove the regulator piston assembly from a minimag valve? I already checked the manual and tried to get it out myself and haven't had any luck. Thanks for your time.

[questionful]

If you can't pull it out with something, unscrew the reg back and push it out through the input hole.

[athomas]

Putting large allen key into the hex head and twisting sideways usually allows it to be pulled out. If not, then do like questionful mentioned and poke it out from the front hole.