Unless you plan on performing other cooling system mods a lower temp thermostat doesn't make much if any difference on the 03/04. You're actually better off lowering the base temps at which the electric cooling fans switch on.
Well, I do need to get it tuned again. Having an SCT X-cal, I don't really have any user options I can do myself.. Maybe it's time to look at another tuner..
It does if you take it to a shop that has the software to do it. Only thing you can do yourself is select one of the 3 tunes it holds. It has no display or parameters you can change like most of the handheld tuners out there today..
It may be possible that there are some thing you can do at home with it, but when I bought the car all I got was the tuner and the OBD-II Cable.