you can make a zetec turbo for about 1000-1500 quid for approximatly 200 bhp. ive done it, twice. ERST manifold will be very tight in a focus, prob best looking for a focus rs manifold, your right in thinkig your standard clutch and gearbox wont cope, assuming its an ib5 box, an rs turbo clutch would do as a minimum measure. The best option would be amanagement change to somethig like megasquirt, with an upreted fuel pump and bigger injectors. hope this helps mate.