Hissing from my marker

I bought a 98 custom a long time ago, but never really got into the sport. I recently decided to make a few more investments, and try and get back into it. I just bought a new barrel, a stock, trigger, cyclone feed, and a bunch of other gear. It all works well. I got it all installed with no problems, except for one. This used to happen too, but now it's actually bothering me a lot. My gun is definitely leaking CO2 from somewhere. I can feel a little coming out of the velocity adjuster, but i think that it's coming out from elsewhere too. I oiled all my o rings and they all look fine to me. I think it might be coming out of my banjo bolt for my cyclone feed too. I'm going on a big woodsball outing in a couple weeks, and I'd like to get this fixed as soon as possible.

Any tips or tricks or advice are welcome. I don't think this is normal, but I could be wrong. If completely necessary, I could upload a video of it to youtube or something. 

Thanks. 

I'm not cocking it before i put the tank on. The banjo is tight. Maybe it's the gas line, not the velocity. I just felt air coming from the general area, and they aren't too far apart. I just replaced my power tube and installed a cyclone, maybe the gas line isn't tight or something. But if i tightened it anymore, it wouldn't line up right when i put it back in, but it was still pretty snug and tight.