Are you sure there legal. Remember, every time you rng up, you get a different answer. in the new regs, it states it must be mounted, and in an enclosed box.
Personally, i'd say get the stcok CAI and a KnN panel filter, It'll imporve by more than the pod (did on my VP) and won't bring anymore unwanted attention to your car when the cops ask you to pop the bonnet.
btw, my VP 5L had an increase off 15rwkw with a VS CAI, KnN filter, and a SV90 computer(HSV).