I agree and disagree. Speaking from experience I know a stock RS can go past 120 in the flats on an open road because I did it in mine when it was 3 months old and unmodded. This was not a downhill run!
You are totally right about not hitting 140. With CAI,Stromung Cat back, and copper plugs I've been up around 130 (based on rpms, since the speedo ends at 120!!) To hit 140 would require quite a bit more HP with the drag of our car. For people's reference, it will redline in 5th at about 145.