New member. Having issues with my 97 f150 4x4. The dreaded 0401 code appeared about a week ago. Checked Egr valve with vacuum gauge. As vacuum increased truck began running rough. Held vacuum.So concluded EGR valve was working. Suspected the DPFE sensor, an easy fix. Reset CEL but after a short drive it came back on. Checked new DPFE with multi meter. Checked good at about 1 volt no vacuum and 3 to 4 volts with increased vacuum applied to EGR valve. Next pulled vacuum hoses off EGR regulator solenoid. It was my understanding the should be vacuum to my source line. At idle I have none and even when engine is revved up above 2000 RPMs still no vacuum. Traced source vacuum line to a plastic junction block on passenger side firewall. Checked vacuum line from junction block to solenoid with vacuum gauge, it is fine. Line continues behind the battery and into the fender wall. Lost. Don't know where the line goes from there. Am I on the right track or am I just going insane? Help!