for turbo you need a exhaust manifold, turbo, some kind of management system, inlet manifold, intercooler and pipework, and you will need upgraded pistons and lower the comp ratio if you wanna go above 10PSI of boost.

not many people put throttle bodies and a turbo on a zetec.

turbo-ing DIY can cost as little as £500, but if you got it done at a specialist its £2000 - £4000.

have you considered the jackson racing supercharger (see www.jacksonracing.com and click on ford focus)