No telling what the driver was doing.
I'm wondering if this may have been a 640 or older 650, they look identical. (Or he was driving in Eco-Pro mode)....at any rate it sounded like you had fun and enjoyed your Italian pal. I actually named my BMW Bruno, while my GTS is called Nino....
With rear dynamic steering and lots of nanny stuff on the 650i, It's fun to jump back in the GTS, take the traction control off and light-em-up. But make no mistake, the 650i is a strong car. The NEWER ones, 2013 up, pump out almost 500ft/lbs of torque and have a published 0-60 time about a tenth of a second or better than the GTS. (around 4.4 or so)
However, the Mas is ALWAYS the show stopper and head turner and sounds soooo much better than a turbo'd car. Even the new Quatroporte with forced induction retains that F1 / beast music flowing out of the tailpipes.
Drive safely. The next time you meet you're Beemer pal, he'll probably have traded it in for something Italian...!
2012 Gran Turismo S AKA-NINO
2013 BMW 650i AKA - Bruno
NSX-(sold :( )