Bigger engine time!
If you were to take the Cat off you would have much beter throttle response and the car would rev more freely as there is less back pressure, you can get a sports cat but then the money on that could of been spent on the straight pipe and ecu trickery.
Remeber that the higher the litter engine the better response to modifications, so you might see a couple BHP from the sporty sounding exhaust on your 1.4 (and a really rubbish torque peak, so bad for if there is weight on the car) in a 1.6 (16 Valve is good if you can afford insurance) or 1.8 (pick up from an engine refurbishment garage or ebay) you will see much better gains from the cheap mods. Try the BHP calculator
http://www.torquecars.co.uk/Tuning/engine-mods-power-gain-calculator.php
for your car, you can get the BHP of your car from
http://www.bosal.com/ select your langauge then country, search for under exhaust for your car model and when you have found the right system on the right hand side will be BHP/Kw.
The gasket has gone on my 1.4 Aztec Si so i will be either sticking a Mk2 quicksilver engine in for economy or a mk2 VTR engine for modability!
Freddy i phoned up PUGsport or whatever the pikeys are and someone tryed to flog me an XR2 engine (1.6) fitted to my car they would charge 700 plus VAT, they would also if i wanted do the head for 450 which isnt bad, but i think ill prob do the quicksilver engine as its a straight swap at a good price, plus i will learn something!
Ring me up for a chat, lots to be said about the piece of *beep* PUG.