You can get a high-output tank that will feed your gun fine. I think they're a little more expensive though.
You should polish your internals. Hit up the Search button on this site and look there. There's also a whole Tippmann Upgrades thread in the Tippmann Pneumatics forum.
Since you're staying with CO2, you could get a Palmers Pursuit Stabilizer or Fatty Stabilizer (I think they support CO2 at normal pressure, but someone correct me if I'm wrong).
Go to
www.model98.net and check out their custom mods. You might find something there useful.