Maybe he's a total purist and was disappointed in the sound of your non S14 engine
Just joking, That's a beautiful car man congrats on the build!
Personally I've come across two other guys in G80's on the highway when driving mine, that didn't look at me or wave or anything even in traffic side by side. Some people are just minding their own business and not interested in being part of a community or what ever I guess. I had a guy in a new M5 do the same thing, in fact he actually shook his head at me for some strange reason. Maybe he thought I was looking for a race or something which I wasn't. We were in traffic in Brooklyn.