[Daox]

True, warm air will cause ignition retardation. In some engines this will happen faster than the benefit from the increased load (and reduction of pumping losses). In other engines it will happen slower than the benefit from increased load and you will see benefits from it. It may work great on some engines during the winter, but since ideal intake temps, for example, are around say 80°F the benefit is negated during summer. The point is there are too many variables to have a blanket statement that says they do or don't work.