The stock ECU already has throttle rate enrichment and leaning out, so it shouldn't be an issue. When you romp on the throttle, it adds fuel based on how fast the TPS voltage changes to compensate for the time it takes air to get from the MAF to the TB. It does the opposite when you drop the throttle, to minimize backfiring due to fuel being dumped in after the throttle is closed. DSMlink doesn't really let you tune that parameter, but it doesn't seem to cause a problem. I don't know if Keydiver fiddles with it or not.
There is basically a range of AFR's that will ignite using a spark, and 16.5:1 is about the limit of spark initiated combustion for gasoline/air mixtures in an engine with compression as low as ours. Higher compression N/A motors (or using lower octane gasoline) can push it a little farther, but beyond about 17:1 or 18:1, the mixture will no longer ignite just using a spark, unless you use special tricks like "stratified charge" (like in various Hondas), where a small amount of rich mixture is ignited, which is then spread into the lean mixture in the cylinder. This only works under low load conditions, and low pressure/density in the cylinder. Mitsubishi has an engine that does the same thing, except that the intake valves are arranged to cause vortices, which concentrate more fuel in the center near the spark plug.
Higher loads and higher cylinder pressures/densities speed up the wave of ignition, until it approaches and exceeds the sound barrier, at which point you get a shockwave, and voila - detonation.
Beyond that, you are basically limited to compression ignition (and direct injection) as used in diesel engines (basically, intentionally causing self-ignition at high pressure and temperature), where AFR can be pushed up to 65:1 and beyond. The effect is basically dependent on how close the oxygen and gasoline molecules get to eachother (pressure and AFR can both accomplish this) and how energetic they are when they smash into each other (temperature). Basically, it's all about statistics, and how likely it is that the molecules will run into eachother and react, and whether others are close enough to cause a chain reaction.
I'm sure you all needed to know the science behind "deflagration" vs "detonation" /ubbthreads/images/graemlins/devil.gif
Basically, beyond 16.5:1, the spark plug cannot ignite the stuff in the cylinder. The leaner mixtures can create almost as much power as stoichiometric AFR's (14.7:1), about equivalent to the rich mixtures used under high load, but the mixture uses significantly more air (some of which is just used as an inert working fluid that absorbs heat and increases pressure, similar to injecting water or steam) and less fuel, resulting in better economy. Basically, it works because the extra air is free and fuel is not. If there were such a thing as "air economy", the lean mixtures would come out worse.
