UPDATE 4/20/08: Here's a new tip for some of you. Pay attention to the depth that you press the endcap back into the housing. Different depths of the endcap change the spring force to fuel flowrate equation. This just means your ECM will have to send a higher or lower duty cycle to get the same fuel flow as before. If you understand this concept, you can manipulate the system to work in your favor. If not please refer to the original picture up top and try to mimic the stock depth of the endcap. Many programmers (read: smarty for dodges & EFIlive for Duramax) change not only the allowable commanded duty cycle but also the response time of duty cycle correction to error in desired vs. actual rail pressure. HAVE FUN!