Cutting through all the techno babble and hoo haa thats been written so far by everyone (I just sit here scratching my head with all the babble). The bottom line for you is that I hope all this works out for you chap and you get the car that you desire, I agree there is a good car in there but I have to say why should you sell a kidney on ebay and your soul to the devil to pay for it?
Thing is that for me sat on our drive way is our Boc, I have to say after 18 months I am less than impressed with it in some ways and behind it the Focus RS, 6 years old, amazingly reliable 250 huffing and puffing ponies under the bonnet and it is quieter, rattles less and does not drink oil like mad. No issues with anything, just plods along, last month it has been serviced and MOT'd and not a thing wrong apart from new cam belt pads discs etc. Small upgrade on the pads and discs and a caliper re furb but that was it.
Do have to wonder about the 1.4 TSI, you can write all you like, surmise, guess, technobabble for ever, but my personal opinion is: The small capacity engine with twin charge; was it desgined to just fill a gap in the market and be all eco friendly giving reasonable power for little running costs and not be massively over engineered for tuning purposes possibly? Everything is on a budget these days, times are tight no matter who you are, The dreaded home techno tinkerer starts playing with the car squeezing out more and more from a small engine, reality is at some point its going to go "Er scuse me mate Im not quite big enough for this!" Shame but there it is. Final thought, 1.6 TSI? or 1.8 TSI? that bit bigger that bit more capacity? could that be a better option
After all you cant squeeze a golf ball through a hose pipe can you?