Alright guys...completely new to the site so not sure how it works..

I've got an 07 Focus ST currently running a stage 3 conversion by pumabuild ( I've heard their not great) but was done a few years ago. Basically the plan is to get it to 400bhp (currently about 310-320 bhp) what is the best way to go and what problems might I have on the way? I've heard injectors/turbo and cams might be the way.

Any help or advice would be really appreciated.

Also, anyone on here from Essex area. As I'm new here too. Cheers