Very happy with my result - many thanks to Jez and the team, plus chirag1988 for organising it.
I went from 269.9 up to 283.2 on my 04 which has the plenum spacer, velocity stack, Y-pipe and drop in K&N air filter.
I feel my Zed is now more lively and seems quite a bit smoother to drive. Dropping a cog or two for a swift overtake is even more effortless, and the low to mid range driveability (can't think of a better word) is lovely.
Had to be careful on the way back home as it was all too easy to creep up over the speed limit.
It was great to drive before, and now it's even better. Love it!