Usually lighter exhausts & wheels. As
MKMD428 mentioned, the TSI engine can be remapped but the limiting factor would be the DSG since it is only limited to 250NM (CMIIW).
A stage 1 APR remap will bring it to bout 125-135 bhp/160-168 lb/ft, just under the 250NM limit on the DSG.
However there are lots of Jetta guys that are doing way more than and seems to hold up fine, these DSG loves to be driven hard and hates creeping on traffic. Do it on your own risk tho hahaha
It's a very driver oriented car unlike the Polo TSI, might be too hardcore for him considering the short gearing and raw feeling aka substandard NVH on highway ahahahah.