Rob: The fans' on and off points need to be set via software, either microtuner or one of the software packages. There is no rheostat. (The software approach is more reliable too anyway)
You can TECHNICALLY adjust the a/f ratio with a microtuner, but have only limited choices and effects:
1. Load the complete preset program that comes in the microtuner, with no knowledge of what you are loading. This obviously ONLY works with a PURE stock vehicle. The microtuners, as a matter of safety and liability control, will not even work if the vehicle's PCM configuration has been altered at ALL, AND of course if the vehicle is NOT stock, the settings in the micrtuner could destroy the engine or do grevious harm to it.
2. In theory, you could use the microtuner to MANUALLY adjust the a/f ratio (The Predator allows this, the Superchips does not), but the manuals warn you against doing this without (a) expertise and (b) the use of a wideband exhaust gas sensor. If you try to do it blind, you are playing with fire, AND you will be almost certainly unsuccessful anyway without exhaust gas readings AND a dyno to guide you.
In addition, you MUST get the COORECT microtuner for your specific year and model vehicle. The microtuners that work on the 04 SSR do NOT work on the 05 SSR, and vice versa as well.
To repeat my statements in earlier postings on microtuners versus software, the microtuners are ONLY for use when you intend to leave the vehicle otherwise purely stock (except the Crane microtuner which can handle a very narrow range of aftermarket Crane (only) parts). If you intend to make physical changes suchas exhaust, intake, cam, etc, a microtuner is not designed to handle that.
Also be aware (you are warned) that the microtuners in general achieve some "cheap thrills" "effects" like barking the tires on upshifts and shorterning and hardening the shifts, but most go to a point that in my opinion shortens the life of the driveline components, especially the transmission inetrnals. Any comptent and truly experienced tuner will tell you that the factory tunes cannot be improved by "up to 20 or 25 hp" by simply advancing timing or altering a/f ratio generically. You need to make PHYSICAL changes to get that magnitude of REAL horsepower. The fundamentals don't change: to get more power, you need to move more air through the engine and add correspondingly EXACTLY the correct amount of additional fuel. That requires physical changes.