Originally Posted by flatliner
Actually the air temp can scramble a base pattern, I know as I use resistors (yes i am cheap) when I race depending on the weather and temp. cooler days need less fuel. even 5 deg farenheit can make a difference in base settings of an easy 20hp on a tuned system. you need to optimize for different weather patterns and reprogram your rig on race day to those patterns.
The goal with using a tunable EMS is to tune for the different readings, not fool the computer by falsifying the readings from the sensors. You want the computer to actually read the sensors and compensate accordingly; not distort the sensor's reading to trick the ecu into doing something that you haven't properly tuned it for.
Also, you actually need more fuel with cooler air. Cooler air is more dense, which means you need more fuel to compensate for the additional air.