F150 V6 4.2L Hard to Diagnose Engine Misfires
 

Been a common problem for years and recently got one in the shop for the concern with the EGR port plugging up and then dumping all the egr into the one cylinder that is not plugged causing a misfire off idle. Many know of this concern but I have yet to see a good example of it. I show you some easy diagnosis before you pull the upper plenum to inspect the ports.