My Impact MK2 is shooting accurately again after losing some speed due to the cold temperature. I kept my Reg/HS the same but I opened up the valve by 1/8th of a turn. That seems to settle the gun and I was able to tag starlings out to 100 yards consistently again even though the slug was traveling slower at 967 fps from 984 fps previously.
I am glad it is so easy to make adjustments (once you understand) with the FX Impact guns.
Enjoy.