I am completely at a loss now. My engine light came on several months ago. When I first checked it I got an EGR Excessive Air Flow and Cylinder 5 misfire. I started with changing the spark plugs, that didn't work. Then I changed the wires, that didn't work. I have the coil pack and switch to the coil pack both checked for the right amount of voltage, they were fine. I changed the EGR valve, that didn't work. I eventually took it to my mechanic and they said it was the EGR sensor. They changed that and my engine light went out, for two days. When it came back on, I took it back to the mechanic and they said my EGR valve was stuck open, so they changed it again. My engine light was off again for two days and now when the light came back on, I was getting horrible gas mileage (from 18-20 mpg to about 12 mpg). When I took it back they said they checked all the hoses and clean them to make sure there was no blockage and said my spark plugs that I just changed about three months ago were no good and they replaced them as well as my plenum gaskets (just because they took the plenum off). Another day and a half and the engine light is back on again. This time the codes read P100 System checks failed and the same Cylinder 5 misfire. Now they are telling me that I have a bad injector in #5. I am reluctant to purchase this injector because I have up until now paid for work that was obviously not the issue because my truck is not fixed. I am about to drive this vehicle from Indiana to Flroida in 13 days and I need it fixed. If anyone has any suggestions, please help!