Hi mate.
I was in the same place as you six months ago.
Had my hr zed from new with 21k miles worth at best 10k! What do i do?
1.Leave the car as it is but crave more power.
2.Trade her in and throw 25k into a 3 year old GTR with mega running costs.
3.Spend 12k on my car fit a gtm kit and cheat the system!
As rightly said earlier you must want to keep the car long term to make the investment viable.
The downsides are only the obvious: more noise, lower MPG and you wont get your money back!
The upsides are:more noise,mind blowing performance,its still the same car you fell in love with
and much more expensive cars get smaller in the rear view mirror when you put your foot down!
Go and talk to Mark at Abbey Motorsport.