Oh gotcha, thanks. Makes more sense now.

 

this is strange. I wonder if it's not actually turbulent air caused by an open intake tube causing it. I came from a MS3 and the stock intake had fins in it to stabilize the air for the MAF (air-straightener). Replacing the intake that did not have a similar "fin" insert caused very similar symptoms. Even the original Mazdaspeed Cold Air Intake option from the dealer was recalled and eventually replaced with one that had an air-straightener.

 

Yes, that could be the reason.

 

I think the general consensus is that changing the tube at the air meter changes both the velocity of the air (temporarily forcing air through a smaller bell shaped area will speed it up briefly) but more importantly that the air is expected to be organized and pressurized in a certain area. In the case of a Karman Vortex MAF like the old evos / DSMs you are actually measuring that turbulence... so having the air flow straight is important.

In the evo X you may wind up with a higher pressure zone on the outside of the tube and lower pressure on the inside (or vice versa) and the airflow over the wire is then a miscalculation of the total air passing through the tube (since the more dense air could cool the wire more or *possibly* throw off a baro sensor).

 

This is great info. I have been having similar idle issues, and have a cone filter setup. Will look into getting a box for it and hope this corrects the issue.

 

Its easy to test - just stick a piece of cardboard between the filter and the radiator fans.