did they do a 1.3 zetec? wasn't it 1.25 or 1.4 16v's or 1.1 or 1,3 8v ??

Anyhoo, doubt you will se much what ever you do, so do the placebo effect, slap on a k&n fikter for the snorty sound, a stainless exhaust for the right sound and lower it abit so it hanles well.

Slap on some decent looking rims and maybe stick some Fiesta RST recaro seats onto the MK4 subframes so it is a nice place to sit and the whole car should be feeling nice and sporty.

It ain't going to be fast no matter what I imagine, and gaining decent power would cost more than a 1.6 conversion and paying the insurance difference.