I have had both ITG(BDM copy) and the TwinTake now back to standard.
Ill be honest, I couldn't stand the noise of either, I am old(er)!
If the noise isn't an issue go for the ITG without a shadow of doubt my car had issues with the Forge and just would not adapt.
The ITG was so brutal though with Stage 2+ I had to take it off, that and the noise.
I have a Pipercross panel now and yes power drops but its much nicer to drive.
Also I found the engine can get quite dirty with no cover.
The Gruppe B looks nice though and don't forget about the BSH truseal(?)
I am considering getting hold of an engine cover and seeing if I can make it flow a bit better at work, I have access to a machine shop, without all the whooshing but with the chattering, I love that.