I'd check your SFT o-ring, located just behind the barrel. scroll down this page until you see the portion that deals with breaking paint. http://www.zdspb.com/tech/mguide/sho...neumatics.html
Also, you may be over greasing your bolt. This could be a cause because the excess grease gets shot right onto the ball with the bolts forward stroke. For your bad efficiency, start with a new battery, and then take a look at your board settings, particularly dwell. You want that at a minimal of 12 for an HE bolt, with an input pressure of 180. Of course, all guns are slightly different and the ballpark i gave you may vary. As for the bolt and modding it, contact either ATLballaz, or cs900, they both do beautiful machine work. Also, lurker paintball has a bolt called the eigen bolt, and is currently what most of us are shooting. I mentioned ATLballaz earlier, and he is going to be releasing a new bolt very soon here if you would like to look into that. Lurker's supply of eigens is also very low ATM, so if you want one of those, I'd suggest getting on it now as he may not be making more of them. MachineGunCrew is referring to Rhino1XL, he came up with the spring that the newer bolts like pooty's, lurker's, and ATL's bolts use. The spring mod is also the most common mod to any bolt which involves Rhino's spring. Being a new shocker owner, I'd also strongly advise that you cruise zdspb.com and thoroughly read it. It's the bible around here and tells you EVERYTHING about the Shocker, and of course this is a very friendly community that's eager to help out.