I had a similar impression of my M5 v. Stock 997TT.

Here's my two year old thread:

https://www.6speedonline.com/forums/...pressions.html

That was at lot of mod $$$ and HP ago. I no longer think such thoughts. My advice to you is to get at least ECU + exhaust. Stock TT boost does fall off. When modded and in Sports mode, the WOT pull from 3K to redline will make you forget all about your M6.....

Stock for stock, in 3rd at about 6K rpm (about 70MPH), I think the M5/M6 would pull away from stock 997TT and I am not sure it would ever catch up. Seriously. From dig or from slow roll, the TT would be walking away by 3rd gear, but that v10 has crazy pulling power above 120MPH.

 

Perhaps the difference is in the feel of the car. Pay attention to the speedometer because the turbo makes it look and feel quite simple.
I have noticed the difference. While it may not "feel" faster, it is making it very easy to go fast. Just a thought.