Please step on my toes if you don't agree but one thing that factors in often the sensors don't handle well is humidity variations. Over all an engine will produce less power with higher water content in the fuel/air mixture, regardless of temperature, the *effect* still occurs. As the PCM fights to make adjustments to compensate for many changes in altitude and air intake for mixture, listening to knock sensors for timing adjustments, water content and changing especially while traveling distances just throws a curveball to the whole process.
