air intake

does anyone know if the perrin radiator shroud fits with the stock airbox on a 2011 WRX?

I recently bought a standard WRX new from the dealership. After the initial break in period where I kept the revs below 4k for the most part I've started to open up the engine. It certainly seems fast but in brisk acceleration it seems to hesitate slightly above 4K rpm especially in second gear...

I tried looking for a thread to answer my question but I couldnt find one, so sorry if I missed it. I was thinking about purchasing a cold air intake for my 07 wrx limited. I was told that as far as hp gains it wont really make a difference, however I was looking for more to have the sound of...