so reducing the valve stem diameter around the port will increase gas flow and raise fps, at the expense of gas consumption, yes.

but you are simply inputting more energy into a not particularly efficient system. The first mods I do to a 22xx are transfer port sealing (they normally leak) and an SSG, which noticably improves efficiency. A 19" barrel helps a lot too, but it's a bit long.

HTH - JB