Hi and welcome, would I be correct in thinking you were a buddy of Jamjay.
The main problem with power gains in the zed is that the ecu learns them and cancels them out. It is thought however that the early imports such as the one you have will have an ecu that will not do this.
The addition of cold air induction, exhausts and other engine mods should see an increase.
The K series exhaust will be worth considering, you will have change from £350 delivered.
The traders on here will have all the goodies you need, one of them will be along soon.