My friend just got a tune for his TTS, the car boosts a lot but after 4k rpm the boost drops a little, he also got a check engine light.
The tuner said is the BRVs, he also said that they are rubbish compared to the gen1 turbo and that they fail very easy. I was wondering if gen1 and gen2 turbos share same diverter valves

 

They aren't the same, 997.2 goes the with diverters like the 996tt.

you should try turbosmart (click on the pic)

 

Great info thx, rep to you