The 1.4 TSI with 170 HP should already have the same brake discs as the GTI, i.e., 312 mm discs. If that's not your case you just need to get front caliper carriers from a GTI and 312 mm brake discs, the rest is the same.
You can also get the R32 front brake setup, since it's much better, but it also weights much more.
See what you really need. Better pads will do a lot of difference too.
