Can you pin open the valves on the 812? Loving the car but a bit quite when stationary. Done it on previous rear engined Ferraris but not so sure on front engines!
There are several people on Fchat that have done that, some by dealers and some DIY.
Maybe it's worth considering something switchable? I did a 2,000 mile trip in mine in December and even with the standard exhaust it became annoying after a while.
Further update on this. Local garage (pal of mine, dropped the rear tray and removed vacuum pipes. 10 min job and now car has a lovely low down rumble, much more Ferrari and not at all offensive. Well worth the effort!