egr problem 98 e 250 4.2 engine

I Have 98 E-250 Ford Van 4.2 V-6 Has Misfire Code 305. Runs Rought Off Idle About 900 -1200 Rpm Has New Wires ,plugs Ck. Has Spark At All Cylinders When Running Bad , Found That When I Pulled Vac. Line To Egr Misfire Is Gone . My Question Is Why Is It Setting Missfire Code Not Egr Codes And What Is Causing The Code ,egr,egr Vac Sensor ... Thanks Tom

I Have 98 E-250 Ford Van 4.2 V-6 Has Misfire Code 305. Runs Rought Off Idle About 900 -1200 Rpm Has New Wires ,plugs Ck. Has Spark At All Cylinders When Running Bad , Found That When I Pulled Vac. Line To Egr Misfire Is Gone . My Question Is Why Is It Setting Missfire Code Not Egr Codes And What Is Causing The Code ,egr,egr Vac Sensor ... Thanks TomI would say you are getting a random misfire code..is that correct...If u can get your hand under the intake...follow the PCV tube to where it goes into the intake, the elbow could have a hole in it...u won't hear it ..hissing but its there...