Originally Posted by Cobb Tuning
Subarus we are support MAF-sensor based, which means increases in airflow are not the problem as this can be measured by the MAF sensor. The issue is when you change the diameter of the intake and/or how air flows around the sensor due to the design of the intake. In that case, the tune would need to be calibrated so that the proper airflow is determined at each point.
A panel filter could, technically, impact the accuracy of the MAF sensor, but it is a much less of concern than an intake change and is generally not a problem. It could also vary with the type of intake filter. We only test with the stock intake filter, so that is why we recommend using that but you can generally use an aftermarket panel filter without issue.
thanks for the reply!
i've always been fond of cobb intakes because of their provisions for the MAF but life is a lot easier when you can keep things stock and apparently the OE intake is a pretty capable design.
we'll see...i have to keep driving this thing in stock form to finish breaking it in as per the manual but also completely assess what really need improvement.