My brother-in-laws Impulse has the valve core leak, we found a way to minimize/fix the leak, however we haven't put enough time behind the gun yet to see how long term the fix is, but it works. We applied Plasti-Dip, http://www.plastidip.com
, to the valve core. We brushed the Plasti-dip onto the face of the valve core that seals onto the brass valve seat in the Impulse. His valve seat also had some nicks in the brass which we filled with some epoxy. So far the fix has stopped the leaking, just make sure to add some grease to the Plasti-dip to prevent wear. We've put a few days of play behind this fix, and it has held up so far, but if it fails it won't be difficult to redo.
We were originally going to re-machine the valve core and valve seat, but this is a cheap solution that has worked for now.