is it possible to use a head from another zetec like a 1800 or 2.0? as i know that the 1600 is very restrictive, thanks

 

No

 

is there anything you can do to improve the performance without goin to mad?

 

Nitrous!

 

lol not allowed mate, i was goin for a set of cams but i would like to get a bit more out of it, would i see much benefits from having headwork done?

 

It's the same rules for all engines.. (n/a).. throttle bodies.. port the head to flow what you need.. make sure the valve train can cope with it.. choose cams to give you what you want/need.. makesure the bottom end i strong enough.. blah blah.