Hi,
I find the original suspension on the track to be unbearably soft and floaty, whether it's the standard VW or the VW Sport version.
Forget the GTI springs, take a look at Eibach's Pro-Kit springs, Pro-System suspension, or Bilstein's B12 suspension or B8 Sprint springs.
These parts are already making a difference.
The conversion is actually quite complex; for example, you have to remove the shock absorbers from the front to replace the springs, etc., and it's not worth it for VW springs.
Good luck anyway

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Greetings, Marcus.