A lot of people mods cars and don't tell anyone. Fekin idiotic but there you go. Guy I used to work with fitted an induction kit and didn't tell the insurance. Said he'd remove it if the car was in an accident. Yeah, best of luck with that. Car is sitting in the yard of insurance repairer and you're going to go in and start unbolting bits?
So your insurance is void and you end up tens of thousands out of pocket. No big deal. It was worth it to make your car sound slightly different.
Bottom line, if you want to mod a car, buy the car. What you have, quite literally, is a hire car that you're using fora long time. It's not your car to mess with and if you do mess with it you deserve to get penalised for it. How would you feel if you lent someone your car and they modded it without telling you? I imagine quite pissed off?