The weak point on these cars is the DMF and more power equals more wear and at around £400 for parts, clutch kit,DMF and cylinder plus labour isnt cheap. Injectors and pumps are also problematic and new are in the region of £200 and £600 respectively.The basic engine unit is good,however the ancillary components are a nightmare and personally wouldnt tune it.
Ref tuning the 115, the 130 has a larger turbo and different injectors so power gains will be much lower.