Well, induction kits work well on some cars but not on others, not sure about the 1.4 RT?!
You will never see a big increase in power, but you can get improved engine response and it will usually pull more strongly and rev freely.
Make sure you have a good supply of cold air flowing around the filter though, as gulping hot air from the engine bay can cause the car to bog down at low speeds.
This is a pic of my old 106 GTi >>>
http://members.lycos.co.uk/Pug106GTi/106_induction.jpg
Note the cold air feed pipe at the front.
On this example, the cone is near the front of the car and has a good cold air supply, so I never had any problems and there was a definate performance gain.
However, on cars where the filter is tucked near the back of the engine bay and/or there is not a good supply of cold air it can cause power loss at low speeds due to hot air being dragged in.
Oh yeah...
Youll get a superb induction roar too!