response from jack in another thread
"You will get a tiny puff of air each shot as the piston moves up and down. The hole is actually there to allow the piston to "breath" as it cycles up and down and the volume between the bottom of the piston face and top of the adjuster screw increases and decreases.
If the puff of air is a propper puff of air, then the first thing I would do is replace the #008 o-ring inside the top of the adjuster assembly with a new #008. This is a bit fiddly and easiest done with the adjuster split in half and the old o-ring removed and replaced from the INSIDE of the adjuster top rather than trying to poke it down the hole in the top that the piston shaft goes through.
You can also replace the #16 o-ring on the top of the piston with a 14x2 o-ring if you feel the piston o-ring is a bit too loose in the reg body."
Maybe that'll help
WTB RL Shocker NXT, Gold SP Epiphany