I have a standard air box here, yours for £10 plus postage?
Yours looks like version 5 with the facelift front end. The best way to confirm yours is 99-00 is in the engine bay. On top of your inlet manifold, you have a black square coil pack, if it's off centre to the right of the manifold then it's a version 5. If it's absolutely dead centre, then it's a 4 that's been face lifted.
On the plug and play prodrive kit... If you have all the bits that went with the PPP kit then you can fit them and the ECU but you will need to get your keys reprogrammed to the new ECU, which the last time I checked was £100 (4years ago).