i would say just the turbo and exhaust as the fuel pump and injectors are superb.
We didn't even have to change them for the stage 3.
And internals are stock on our demo car.
Hope this is of some help,
Dean

Leon Cupra R - 262BHP/350lbs/ft
H&R springs (Needs coilovers!!!)
Forge Hoses
Tarox discs/Taroc Corse pads
Needs for bits!!!!!!
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