Need some air help!

i just installed my 1/2 blitz valves, the air is bleeding out of the cylinder back into the lines. I know i need to put a check valve there! (Where can I get a check valve to solve this?) Would i be better off runing 150 or 170 psi on a honda? And I know you can only use 2 wires on the valve and it work, but what is the other prong for? I had to have 2 grounds on each side of my 3-way valves.