I have recently purchased my wife a 2002 Chevy Trailblazer LS (4.2L I-6). We love it, except for the fuel mileage. My questions are will a CAI (or stripped stock box) and a lower thermostat have a positive effect on both performance and fuel mileage (or at least the latter)?
I know what options there are for both, I just want to know if I have a good understanding of both of these upgrades in that they will positively affect mileage and performance.
They will both increase your gas milage. However, in the cold weather, a colder thermostat can sometimes have a negative effect on milage because the engine has trouble getting up to the optimum operating temps. At least that is how it is in my experience. I see you are from Florida though, so it shouldn't be a problem.
the 160* I had in my Bonneville did create problems, but I have no had any with the 180*. I am trying to find a Trailblazer/Chevy forum where the exact technical aspects of the engine are discussed in more detail in regards to these modifications.