I dunno, it's a basic 1.3 engine that has a turbo bolted on. At 15psi boost it was rolling roaded and realistically produced ~165bhp. I run it as a daily so reduced the boost to 10psi - at a guess maybe 140bhp? I'm sure this Fiesta ST guy is a poor driver too which helps.
By far the best element of a boosted Polo is the sleeper value. So long as you don't go mad with exterior mods, to most it just looks like an old Polo. Then BAM, boost :-)
I think Breadman has put it well - there are many weaknesses, but the fun factor is excellent.