These day's your better off with a zetec, pinto's are fetching silly money (although they are still very tunable, at a cost), wheras a zetc is penuts compared to them. If you really wanted to, I reckon an ST170 n/a could push out 250+bhp but it would be a full on competition engine (with a pricetag to match), keeping it simple I reckon 210-220bhp should be possible. As for 250-300bhp zetec turbo, look for the zetec turbo on the cheap thread cause their loads of info in that thread, hang on I'll find it for you if you want. Have you though about an XE redtop? A bit more expensive than a zetec but people say its easier to tune.