If you REALLY want to hear it, get a Psychotty. Cutting the 4" hole in your firewall takes suction of cooler air from your inlet at the base of the windshield, and also provides a path for turbo noise to get interconnected with your A/C air outlets in the cab.
Personally, I've decided I prefer the "dry" BHAF/MHAF style air filters over the K&N or other oiled filters. So you might want to try the BHAF before you go "all the way" and start cutting holes.
If you want to stay with your stock airbox, then cut about a 2" or 3" hole in the firewall at the same location as for Psychotty, and a matching hole on the inlet side of your airbox. Then connect your airbox inlet to this new air source with vacuum cleaner hose or similar. Should have a similar impact on "piping" in the noise, and will increase cool air into the box.