I think that:
In any operation: Open Loop, Closed Loop, WOT or Partial Throttle, a stoich mixture along with correct ignition timing will give better HP output. Thats what you are looking for when tuning a car...configuring the ignition timing along with a stoich mixture given the octane of the fuel, air temp, cyl press, engine temps, etc.
We only run rich mixtures, colder plugs, high octane fuel...to prevent detonation.
Take the mazdaspeed protege as an example. Its power output problem is because of a rich mixture. What did Mazda do? Lean it out a bit.
The reason that our cars runs 14.7:1 instead of 13:1 is because of emissions, efficiency and power output.
Anyway, @ 13:1 the car runs hotter even if its richer than 14.7:1.
