Man i am telling you just like the other guy something is done wrong to it.I know people with setups like yours and they get 20mpg like it nothing and thats with a automatic so a stick is 2-3 better mpg right anyway.With your mods i am telling you high teens should be no problem and with all of the black smoke and all of that.That equals your money going into the air because black smoke is unburned fuel.If it was tuned just right it wouldn't smoke hardly at all ever.