Here is some info from Cobb tuneing's website.
Q. I have XYZ intake, do you have a map for it?
A. We can do mapping for quite a few intakes that are predictable. We have maps for the original(black) APS, Injen, and most of the short ram hot air intakes. The Blitz is about the only short ram that is not predictable. The car may not be as smooth or might miss out on some power since we have to tune even more conservatively with most of the intakes, but it will be safe, and run better than the factory ECU. Also, let us know what specific intake you have. We have had people order the map for the APS intake when in reality they had other intakes. Needless to say the tune was far from optimal. So far the AEM is about the only intake we have seen that is not predictable. We could make a map for it that would make sure that the car runs rich rather than lean, but the benefits would be far less than that if the customer just removed the intake and used the factory unit. We even have to do that on the dyno for the AEM intake. Also, even if the intake is advertised as not needing correction, causing no errors, or factory specifications, let us know. This is not the case on the intakes that we have tuned that make this claim, they do require correction. Just because the piping that the sensor sits in is the exact factory spec does not mean that there is no turbulence to throw the sensor off. In the end if you want the smoothest running car use the factory air box. If you want the noise and slightly better spool-up, remove the silencer in the fenderwell and toss a panel filter in the stock air-box. On the stock turbo you will make the same power as you will with an aftermarket intake. If you have any questions or want to get the best map, your best bet is to give us the most information you can and let us choose the proper map for your combo.
Here is a link to Vishnu's website
http://www.vishnutuning.com/stage.htm.
Both of these companies know a lot about Subies and neither use aftermarket intakes on any of their stages. If you just want the noise buy a TXS DP, you will hear the turbo (not the bov) and gain some power.