Sorry it took a while to get back to you, did you figure it out?
I cant really remember what I did with the old brake light. I think my GT TDI had a spoiler fitted already, but was different to the R32 / GTi one.
So I removed the old one (inc brake light) and replaced with R32 version, inc brake light, I think.
Just had a quick look on ETKA.
The tailgate is the same part no for my TDI as it is for R32, in fact there is only one tailgate part number listed.
Tailgate:
1K6 827 025 H
Spoiler:
1K0 071 640 K - Normal / non R32
1K6 827 933 D - R32
High Level Brake Light:
1K6 945 097 B - Normal.
1K6 945 097 F - R32 / GTI spoiler mounted brake light
Hope this helps.
Jas