I was just wondering this. Since a MAF measures mass airflow in a given tube diameter could you make an oval MAF housing as long as it had the same cross sectional area as the circular housing?

 

you could, but you would have to do some serious re-tuning because the maf signal will definitely change.

if the air velocity inside the new tube is slower than the old tube (it may be similar given the same cross sectional area, but it will probably not be the same) then the car will think less air is coming in, so it will use less fuel...

this could lead to a lean condition very quickly

 

I am assuming that there will be a required tune. So in other words as long as you are tuning it an oval maf housing would be exceptable?