Davgill, just who or what were you disagreeing with? The last posts before yours was from 07/02/19 - 10/19/19 4 years ago??? No fumes on my '18 RTL with a BIW Cat Delete. Is your F4 windscreen vented and is the vent open? I went the extra mile and Titanium Header wrapped my front tuned pipe and the Cat Delete , but you still can't easily wrap the joints/gaskets.