As I have mentioned previously, the limiting factor is fuel delivery. The mid range you have just now is not all that it could be due to the fuel pumps inability to deliver the required amount of fuel, and the ECU pulling back boost to compensate and therefore stopping the engine from running lean. The same thing will apply in stage two, only with the top end being restricted.
In reality, midrange is not affected that much, but the top end is a lot more enjoyable and the top end being more lively makes the mid range seem more paltry.
It will be interesting to see what you think, but you really should put in an uprated panel filter as the OEM filter is pap/inefficient.