N/A Tuning £2000 For individual TB's set up with Cams 200-220bhp
Supercharged £4000 on the road if you can find a kit in the first place and keep stock internals 290bhp
Turbo Charged £6000-Skys the limit 300-600+bhp

I started a ST170 turbo build (which is on hold due to finances) and even considering i can pretty much do all the work myself i needed just shy of £4000 for parts to hit 400bhp