on the 1.4 there really isn't any point in doing mods for power. the best thing you can do is a full pucka service wih fuel filter and plugs etc to make sure its running spot on.

if you want it to sound nice then a cat back exhaust would be the way to go and then brake and suspension upgrades to make the most out of the car.

BEFORE you do anything though check with your insurance company first as mods usually mean higher premiums and if you don't declare them you will invalidate your insurance and be fucked if you have a crash as they will NOT pay out and you may well be prosecuted aswell.

if you don't mind me asking, how old are you and how long have you been driving/number of years no claims bonus??