There is a good article on tuning the Ford Zetec engine here. But we have just found this site dedicated to Zetec turbo tuning.
Check it out if your thinking of going turbo on your Zetec.
Here is an excerpt
First of all, there is little point in trying to turbocharge the restrictive 1.6 Zetec. It can be done, but as upgrading to a 1.8 or 2.0 will offer a lot more potential for only a couple of hundred pounds more it’s something of a no-brainer. The 1.8 as fitted in the XR2i and RS 1800 is a possibility, although most people opt for the 2.0, which has the obvious advantage of the extra capacity and a wider choice of pistons. The 2.0 is more expensive and sometimes harder to find than the 1.8, but having said that, locating a base engine should not be any trouble at all as it’s quite a common powerplant.