Honestly, the air filter won't do anything. Heck, doing the whole intake really only changes the sound of the car, does nothing for performance. But oh, if you like the sound of a bypass valve...the intake does wonders.
Martin had some rough moments and hasn't had the best history with some owners in the past but I've been dealing with him for more than a year now and he's been great by me. So much so I'm going with him and his tuner to dial in my car. (The modifications are at a point where tuning is beyond my confidence level in knowing I crossed all the Ts and dotted all the Is.)
We're lucky to have all our venders such as DDM, Hahn, Werks, and RPM. They all are supporting our car, a dead model from a dead brand...and that's something to be thankful for. I have a Hahn Intercooler. Got my suspension stuff, fuel rail, and oil return line for the turbo from DDM, got my clutch from Werks, and then my high flow cat, cold side charge pipe, and big wheel turbo from RPM.