The way i would test the valve its self to see if its the valve, if you have a vaccum pump for like bleeding the brakes. Hook that up to the valve start the truck let it idle, once its idling pull a vac on the EGR the truck should stall, and the vac should hold steady intill you release it. If it works as advertised its not the EGR. If still having probs post it we will nail it down