If your going to build a car stupid quick enough just to beat your mate then don't do it with a polo! A mk2 golf? Sure. My mate had a 1.8T MK2 Golf, 315bhp, sublime car, another had a corrado 1.8T, 335bhp, again sublime!
TBH, you dont seem clued up enough on cars mechanically to choose a polo and put 300bhp through it. Also why 300bhp? Surely your aware anyway that the general 'road' power limit for FWD is around 220bhp. Even chassis wise your looking at spending a hell of a lot to get it rigid enough to take. And the fact that no one has taken a FWD polo using the G40 engine upto 300bhp, there's reasons for that. Stick a 1.8T in it, yeah, make it drive nice, hmm.
Do abit of research, then come back. I have a funny feeling when you do you won't choose a polo.
Sorry, just my opinion.