It's wierd, my truck ran the same at any level with the 22r. the 22re i just put in has a miss at the altitude i am at right now (about 1800ft), but when i get up to the rubicon or Moonrocks is runs great. i am not smart when it comes to engines so i don't know what is wrong, but i am not goin to deal with it right now. when i still had the 22r in it i could go 70mpg on the freeway all day on flat ground with 35's. but when i got the 37's i could barely go 65 on the same freeway.