I fitted up the 390 air box today which gives an extra 60mm resonance length and a tidy bell mouth. Using the seat of my pants dyno I can report;
The hole in the bottom end power delivery made by the cam has been bridged, the off idle response is smoother and the wheelie machine has made a return. There could be merit in too short an inlet tract producing a "double charge" when the mixture mass reverts against a closed valve.
It starts easier, f@cked if I know but it does, simple as that.
It sounds TITS !!! Tourist if you think the insistent, metallic, death vader-esque is the business now, well it doesn't menace or imply, it IS evil incarnate dressed in Armani.