I'm surprised the piston mod didn't increase fps for each pump as it should have increased pressure per pump. To get max numbers beyond the piston mod you'll have to get into the pressure chamber by modding the abutment pin and chamber, but that will require more pumping to fill the extra volume. I'm working on a project new model 880 for a hunting setup that will consolidate the piston and chamber mod.s. I'm shooting for 12 to 15 FPE once done. If all goes well I hope it leads to an aftermarket abutment washer for the 880 that will increase chamber volume and max power but will likely require additional pumping. The idea is to design an abutment washer from steel like the 1977 rather than the "fat" aluminum one used in the 880s which consumes more volume. If you want max power per pump mod the piston and leave the chamber as is. If you want max power with no regard to pump count then both need modding. For hunting, if the first 10 pumps don't spook the game then the next 10 probably won't either. The best solution to pump noise is remove the retaining spring for the pump lever and place felt on the pump handle where it contacts the receiver. If you quite the pump action then most of the time if game is spooked by pumping its the movement verses the noise. A blind goes a long way to prevent being seen while reloading. I have taken a bag limit of squirrels in one evening with an 880 pumping 20 times per shot while in a blind. Paying attention to being quite while pumping is the key.