3406b low power in higher gears

Thanks, i just dismantled it again, took the new piston seal off and put back the old one, turned the screw out a little bit, then reassembled and now it runs perfect. I think when i was replacing the piston seal i moved the piston off centre a bit, then when i was reassembling the extension slipped out. I made sure to centre it this time and applied even pressure when assembling. No more power loss.