I've done 100HP shot rhrough a stock Zetec. I would not recommend anything about 50 without some tuning. My 65HP shot (with tuning) got me into low 14s, with just a cat-back exhaust, udp, and optimized TB.
Frank McCoy aka Mod-deth aka Mid Life Crisis aka SVT Doood aka mcgainer is a SCAM ARTIST
Pre98 Zetec - Some Mods