I don't think these cars need a remap either. I think a good exhaust and induction kit is plenty for a car that people are proving is more than pulling it's list BHP...
Is the warranty worth risking especially with a gearbox that costs as much as this one.
It's all about opinions at the moment. Different people are trying different things, which is great, just be careful or you may get burned.
ED
In the comparisons I have seen on Golf's the addition of a full turbo back exhaust makes little difference.
The stock cat is fairly large for our engine capacity and the pipework is fairly high flowing and 2.25inch in size which is pretty large for a 1.4
I ran 300kw@wheels and 520nm in my subaru with a 3 inch exhaust to give a comparison.
Most people go oversize in exhaust thinking flow will be significantly greater but many rally cars will go from 3 inch to 2.5inch towards the end to keep the gas hotter, hotter gas flows faster and makes more torque as it scavanges the cylinders better. I know of subaru that went down to 2.5 inch from rear axle backwards and made 460hp@wheels and pulled a low 11 Qtr.
You should also consider that the GTI golf's have identical catbacks to the 1.4 twinchargers but can make 200kw@ engine before they need a full exhaust.
Intercooler pipework is another area where people assume big is better. 2 inch pipework from turbo to intercooler can flow about 600hp. If you go larger you just get more lag. The pipework on WRC cars is no greater than 2.25inch from turbo to intercooler.