The star wheel is for the AFC (Automatic Fuel Control) - what this does is it holds back the fuel until there is enough boost. You can spin the wheel all the way forward if you want and what it will do is lessen the preload on the springs so that the fuel will come on a little sooner (lower RPM).
You can get an AFC spring kit that will do away with the double spring set and go to a single spring but if you do you need spend some time playing with the star wheel setting then so that you don't just dump fuel when there isn't enough boost to actually use it (tons of smoke). Plus if you have it set to loose you can run into a situation where you have high egt's and can't out from under them until you back out of it to allow things to cool then get back into it - is that clear???
I played with mine quite a bit and have mine set so that around 1500 rpm it will start to fuel which according to Cummins tech sheets they consider anything under 1500 rpm with heavy throttle to be abuse after that they pretty much point that you can give here all she can take. So I set mine up that way and it helped with the overall egt situation. Now I can plaster my EGT gauge past it's reading but I don't do it as quickly as I used to....
If you are going to do the AFC spring kit I would also recommend a boost control elbow and play with it's setting to adjust the opening of the waste gate. if you have the stock turbo set it so that she can't go over about 35psi as after that you are just causing egt's to sky rocket and not really gaining anything...
