The stock panel filter is large as filters go and will flow as much air as you reasonably need. You could hold off on the K&N panel filter until you need a new stock one. One benefit of the K&N is that it lasts forever, but you do have to buy oil and cleaner for about $10 and cleaning it is a messy job. When you remove the sound deadening, also remove the restrictive horn from inside the fender intake. There is a screw on top that holds it in (from inside the box). Holes help if the hoses are ducted to cold outside air. Turbo engine compartments are very hot. The easiest way to go is out the front, through the knock out panel that you will see. Test your hot air entry thermostat with a lighter if necessary. Make sure it is closed when hot and open when cold. If this fails, and they do, the airbox gets heated air.

Cone filters make cool siren sounds if you are into that, but you have to put the filter out of the engine compartment or fabricate an insulated area.

I doubt there is any power gain from a cone over a properly set up airbox, but I do think that the stock airbox could be worked over a bit more than the usual mods that you have done and that I have added to above. I might take a diesel airbox top and turn the airbox sideways and redo the inlet and outlet hoses with larger and straighter ones. It will be a bit of a project. And then I'll start thinking about a bigger air mass meter.

Philip Bradley