How does the IAT sensor and the map sensor relate to fuel millege. As far as cleaning it goes. How does this help.

 

Map sensor tells the computer how much boost the engine is seeing. The computer then reads that and decides how much fuel to throw in. The IAT sensor tells the computer the temperature of the incoming air. The computer reads that and decides on how to adjust the fuel/timing. That's in a nut shell of course. If the IAT sensor is dirty, the computer won't get the correct reading and could start putting in a lot more fuel than what is needed. If the map sensor is messed up, it could read real high boost at low rpm's so the computer throws in a bunch of fuel when it's not needed.

 

http://www.smokindiesel.com/Technical.htm