Actually most engine management systems will increase/decrease spark several degrees depending on air charge temperature (usually as a function of two tables that multiply together --- not sure why they use two tables, but they seem to always do that). More spark advance typically means more power (unless you get detonation), so in theory it will provide more power and force you to run more octane to prevent detonation.

The a/f ratio typically primarilly looks only at the MAF readings and is not tied to the air charge temperature (ACT). The MAF will read "mass air flow" and will adjust for temperature on it own. As a result, the a/f is not tied to the ACT except and the car should not run richer if this mod only screws with the ACT sender.

Nevertheless, under some conditions, the ECU will read the ACT and see that it is out of a specific operating range and command either more fuel, less spark, etc. This is usually on the high end though or during the start up sequence.

Bottom line -- try coming to MN and see if it makes a noticable difference to your performance (its about 10* right now). You need significant hp increase throughout the rpm curve to notice anything. This mod will not do it for you. Instead you risk running on a hot day sometime, having strong detonation and losing a piston. Just some thoughts.