I had been having problem with mileage and the truck would ping under slight acceleration. Under very hard acceleration it would ping very badly just before shifting. Milage. I started using mid grade gas and it help deter the pinging. Then my check engine light came on and my mileage drop to about 10 mpg and the ping was back in full force. Trouble code all pointed to the EGR valve, swapped it twice. Then swapped the DPFE sensor, no help. Swapped the DPFE sensor again, problem got a little better and check engine light went away. Mileage came back to normal. Swapped both O2 sensors, no help. Still pinging. I was getting ready to clean the throttle body as suggested by many. Then while reading about fuel injection systems it was mentioned that the fuel filter could cause lose of mileage. So I know it had been quite some time before I have changed it and decided to do so this morning. I still don’t believe but since then the pinging at easy acceleration it gone and very little just before it shifts on hard acceleration.