They can say what ever they want in their warranty that's the whole terms and conditions they set out. If they say certain things are not covered then they wont be.
EG as per Subaru NZ website
What Is Not Covered
Wear and tear caused by use of the vehicle for racing, rallying, speed trailing, hill climbing or similar activities or competitive events.
so don't expect it to be covered.
Anyways it is sweet to see someone modifying a new car as most wont, would be sweet to see how it goes on the track and just how much power it puts down in its current state on the dyno