Kiwirog quotes 175-180 bhp can be achieved on a plenum but I think you'd need some pretty aggressive cams to get there. From my limited experience to date, the thing you need to consider is how much day to day driveability you are prepared to sacrifice in the quest for ultimate power? Mine only has mild phase 2 cams, it goes well but currently it's not as pleasant to drive through traffic as it used to be. To that end I am booked in at Emerald in 2 weeks time to let Dave work some magic....hopefully! I'll let you know how I get on.
If you fit an Emerald you won't need a FPR (Rog did me a good price on my Emerald by the way).
You'll need to budget about £400 for the mapping to be done at Emerald's rolling road.