My 4 is stock, too. Thew only thing ive done is adjust the velocity (280fps), and ran it in PSP mode...
with a 70/4500 tank filled to 3500 psi, and a Rotor attached, in 35 degree temps, I was getting a hopper and 7 pods out of that fill.
Judging by what you stated, that seems perhaps a bit more efficient than yours.
Check your FPS first, you may be shootin hot, but you should be able to adjust your Dwell down a bit to help your cause. Being a first time Etek owner, I havent messed with mine yet, but your owners manual explains it in detail