I don't think they warp, I don't think it's possible to warp cast iron, it's more the standard TTRS discs are both the same hand/directional vanes so one side runs hotter than the other.which isn't ideal when pushing on, you'd probably never notice in a mk5 gti unless you track it.
The vagbremtechnic carriers that allow use of the 340mm TTS disc may seem a tad expensive but the TTS discs can be had for about £80 ( Brembo) a pair where as the the TTRS are north of £300.
I bought my kit bit by bit ,and I was lucky to find the vagbrem carriers and j-hooked discs lightly used locally on eBay for about £120 ( Bargain ) the seller thought they where warped after a trip to the ring,but what he was experiencing was probably pad deposits because Iv never any problems with them,
great upgrade