I have had both the ITG and Revo intake - currently have the Revo intake in my 2007 S3.
The forge, meh well, haven't heard great reports on it and people moving from forge to the likes of ITG/Revo.
My ITG pulled 4-5g/s more air than the EVOMS intake when I first got it (Revo initially had the EVOMS intake in their Cupra K1 car before the ITG). The Revo is pulling 9g/s more than my ITG.
1 g/s roughly equates to 1.25bhp so thats an increase of 11.25bhp over the ITG
Revo for def!!