Turbo it.
run it slighly higher compresssion and a small turbo will make it less laggy and should help to keep you pointing in the right direction as the power will come on a lot smoother and not so harsh as with bigger turbos.
Swap pistons for forged ones.
rods are good for 250bhp if you get them shot peened and arp bolts but rods from the ststes are cheap as fu*k at the mo.
meagsquirt managment on a fiesta turbo inlet with adaptor plate with beige injectors.
loads of fiesta stuff on ebay megasquirt cheap and loads of stuff for the zetec on the dedicated forums.