I have a EGR issue with my car according to my SEL and will be taking it to the meachinc in a couple of weeks to repair. A friend told me to unplug the vacum hose that plugs into the top of the EGR valve until I get it addressed and the engine will not ping and run as rough. I doubted him but he was right. Why is this so? My car is the 98 Ford Taurus stationwagon with a bad headgasket. With the vacum hose pluged into the top it shakes and shimmy for a long while, unpluged it does it for a few minutes and then it runs like it did before the issue arose, plus i am not seeing any loss of fuel milage.