I took a load of pics to make a 'how to' topic on this, I haven't started it yet

Surely if there is a restriction and the turbo can't efficiently suck in more air then a bigger allowance of air would help things? Like sucking on a straw as fast as you can, then doing the same but by covering the end of the straw slightly with your finger. 

 

I'm not entirely sold on this though, not for the price anyway haha

 

There isn't any restriction, that's why it doesn't do anything. Stick a piece of 6" soil pipe on if you like, it won't make a blind bit of of difference.

 

The science is really simple; your dog accidentally sits on your hose pipe while you're watering the garden, you notice the reduction in flow so you frantically start twisting the nozzle to increase the flow, you then remove the nozzle altogether all to no avail, your dog starts looking at you strangely because you're acting illogically and stupidly.

 

As I've previously mentioned, the volume of air entering the intake cannot change no matter how large it is, there is a minimum size below which there will be some restriction but the standard PD130 intake is larger than this.

 

It is entirely possible that the PD160 intake exists for homologation purposes and that it is useful when larger turbos are used, a simple calculation of CSA will yield the theoretical flow capabilities, however the hose analogy remains, the largest pressure drop is probably in the intercooler, not the intake.