Congrats on the first post ...... as they have said, keep your foot out of it, don't exceed 2,000 rpms. If this continues, take it into the dealership (still under warranty?) and have them check it out. Those $9.98 chips that say it'll increase HP by 5% and mileage by 5 - 10 mpg are a POS.
i bought one on ebay. "White Lightning" i think it was. tied into wiring of maf sensor or coolant temp sensor. blocked government restrictions in computer. supposed to make it run richer when needed and less gas when not needed. mpgs supposed to greatly improve. toyota maf sensors too complicated for it and to get to coolant wiring i had to take off entire intake manifold. pita!!! never installed it. if i get time later i'll take pics of it and some instructions.
^ That's actually a myth. When the tailgate is down, air coming over the cab presses on the back of the bed and tailgate pushng the back end down. If you leave the tailgate up an air bubble forms in the bed and air deflects off of that as it passes over the truck. Put dry leaves in you bed and you will see what I mean. That, and I watch WAY too much Mythbusters
My 2005 access cab 4wd automatic gets apx 20-21 mpg consistently if i am a little careful with foot on accelerator. BTW, have a hard tonneau cover over bed. They can be pita cause i have to take quad on trailer, but I think the cover helps mileage. :thumbsup: