[jpk]

For starting, the DME retards the ignition and cycles the fuel injectors a bit longer to richen up the mixture. As it's warming up, ignition and fuel gradually go to normal as the DME reads higher temps from the temp sender.
There is a fixed amount of air that bypasses the throttle all the time (the sealed air bypass adjustment) and for cold idle, there is an auxliary air bypass controlled by the DME. That's all it takes. The DME reacts fast enough to let it idle at normal speeds when it's cold.