I was thinking of leaving the bottom half of the airbox in and putting a heat shield around the top, with the pd160 intake in place
 
I have a pipercross at the momnent but I'm not convinced on their filtration quality.

I would also like a little induction noise.

Would you see any gain from a cone filter over a panel filter?

I am aiming for the elusive 150 bhp from my PD130 on the standard map.
 
You could take the airfilter out altogether but if the ECU requests X amount of air and is recieving it with the stock airfilter no matter what you do to the airfilter system the engine is only going to suck in X amount of air and no more. You might want to read THIS