to be honest i'd keep the pipe and box and put a new filter on. especially if thats a steel mesh filter.
have a look for an apexi filter or anything that takes your fancy.
i also like the BMC CDA not really used on the zed, its a universal kit, but it comes with a carbon cyclinder airbox, very nice bit of kit.
lots like the normal pop chargers, other kits to look at would be the AEM or similiar. loads of choice, all offer about the same gain in noise (no real power to be had out of any of them, not to a noticable level.
for something really unique and different that no one runs on the zed is the PMC
http://www.prmracing.com/
meant to be an amazing sound and very popular on the S2k forum