bad gas mileage

hey guys, just wondering.. I put gas in today and the range only got up to 470..? When I brought the truck home it had just about half a tank and only gave me 200km to almost empty ( the gas light did NOT come on). I have about 240km on truck. So right now with a full tank of gas my range says...

I get 7.0 mpg city, 8.0-8.3 highway!! No matter how i drive( heavy foot on gas pedal or light foot) i am getting almost the same MPG!!!! Ive changed spark plugs! What other things should i check!?? EGR and Oxygen sensor could be the issue?? How can i know if the oxygen sensor needs changing if...

Hey All - So over time, mainly in the last 2 months I have been getting 9-10MPG around town and on the highway it was about 12MPG. It used to be 22 and 15MPG. I installed a Volant CAI, Magnaflow/Muflex 18 and I have 2" level and 35" Nitto Trail Grapplers and a catch can if that matters at all...