nice product here skywalker.
About the cool air and rain...here is the details
- When temperature is LOW, atoms move slowly (imagine 100km/h, something like solid material). This means they are closer together.
- When temperature is HIGH, atoms get more energy, and therefore, it bounces back and forth (imagine 500km/h, between other atom) faster, which makes it spaced further apart (something like water)
So, taking the examples above (solid vs water), solid is much denser than water, which means it is more pack (dense).
Conclusion : Cooler air is denser. Driving at night or in the rain, actually helps the engine to 'breath' better, and should improve FC.