Some months back I replaced my Lp and the truck ran great for that time. The truck started to give me dead pedal so I took it to a diesel shop and was told my vp44 is going out. I had it replaced but within a few weeks the truck started acting like air was in the line. I took it back and they couldn't find an issue until a week later when it stalled out. they told me there was a bad sensor in the new vp44. What would cause the failure?

 

Where did they get the replacement VP from? Was it from a certified rebuilder?