It appears to be a GP pulsarz "flow sensitive unloader" but espec attached something on the outlet. I believe it is what drops the pressure like the K-7. I've never used the K-7 so I can't compare, but so far, this is treating me well. I'm in the KEC biz and not having the initial blast when the trigger is pulled is somewhat priceless!
I do seem to be having a problem that I thought was unrelated. My thermostat seems to stick. I'm running a 110v w/ adjustable thermostat. The heat will activate, rise to desired temp, then cut off, but not re-engage when temp drops. If we turn the dial down to off then back up, the heat activates. I thought it was the thermostat, but I replaced it and the new one does the same. I thought it was the unloader messing w/ flow sensor, but that doesn't seem to be it... I don't know how this could be caused by the unloader, but it started on one of my machines the same week we installed them!