I'd like to know as well. I've read maybe one post by somebody running it that really liked it, but I have some concerns about the lack of air straighteners in the MAF housing. If you read the PDF regarding this product on the Corksport site, you'll see he says testing revealed much more low end without the straighteners in the housing, and the measured fuel trims were within spec for Mazda OEM.
Since the straighteners seem to be the concern when it comes to fuel trims, and others running the Cobb and CPE have said their fuel trims shown on their DH were varying, I wonder just exactly how crucial they are.
Mazda engineers felt it necessary to have them in the factory housing without any regard to the amount of air they restrict, but then again they did design the factory air box and the turbo inlet and one of their primary concerns is a wide margin of safety to protect the motor. I mean really wide like almost idiot proof. Just look at the AFR under boost in this car and all the sophistication in the ECU to prevent knock etc.
Personally I think anything in the MAF housing beyond the sensor itself presents a restriction. Imagine having air straighteners inside your nose for instance.
I would also like to see some testing using some different air filters on a MAF without straighteners. Some of the filters on the market have some pretty cool looking engineering behind them to help streamline the airflow to increase power and I wonder if this could be adequate to compensate for the missing straighteners. The APEX-i filter comes to mind as well as some others.
Anyone else care to add?