Hissing injector after AFPR install

Me and a buddy installed my AFPR this weekend. Now when I turn the key and the fuel pump comes on there is a quick hiss like air is escaping. No gas is found or smelled. Also the fuel pressure is held any more. It goes up and comes right back down unless I start the car. We did remove the fuel line to install the AFPR and think it might be a cracked o-ring. Could this cause the noise and no pressure?

BTW the car still starts and runs but it hesitates a little.

Well the regulator was working good when we took it off another car. I did yank on the injectors to pull the fuel rail up. But like I said. There's no gas leak at all. Just the hiss sound, dropping pressure, and car turns over more before firing up.