+1 on moleson10.....use the schrader valve on top of the fuel rail. you should be getting approx 5
si on a guage. I have an 08 XStar with the 6.0 and my pump went out 2 weeks ago... I just bought the $75 Airtech E2044 from Advance, took about an hour to install it, and it's been running fine since then. After replacing the fuel pump you may have just had air in the lines from the previous pump. Mine acted weird at first too until I bled the line via the schrader valve.