Problem with Nine ball Floating valve spring

[Jeffleon]

I have i think a feeding or nozzle issue ever since ive installed the dyna piston head along with the valve spring that came with it. Well every time i shoot my p226, it would shoot normal for 2 or 3 bbs but then the next shot would vent all the gas out, the only way i stopped this was putting the stock spring back and it worked normal except the fps dropped compared to having that stiffer spring. Also ive been using crossman .20s, im thinking that higher quality bbs could solve this since the nozzle is having lag time feeding them.