My reference was a stock moco 96" in my 07 Streetglide to my new 11 stock 103 Roadking, I alternate riding both bikes and there is more top end clatter with the new 103". When I say stock I mean pipes/air cleaner/tuner on both bikes but no motor work. Of course every motor is different but just my observation with my two new ones.

 

sorry valvetrain noise was what i meant , a lot more clatter when warm

 

It only makes sense to me. Less metal to muffle piston sound should make a little more noise.