Does a K&N air filter count as a mod?
If so, installed one of those on the car today.
Instead of simple pop-clips like...pretty much every car i've ever worked on....the GTI uses Torx screws to hold the airbox lid on. Same as my Porsche.
No clips.
T25 Torx bit will take apart most VAG products:
Pop off this hose:
Before/After:
Factory airbox is quite good and will be fine up to Stage 1 power level (300 hp). I don't expect any power gain from this, but it'll allow me to save down the road on air filter changes.