My bike has the Rotty airbox, Arka's, Mapped etc.
At present it has 16 / 38 and I find it dull in comparison to my previous SD which was mostly Std but had 16/40 gearing. 16/40 produces a top end of about 140 MPH, power wheelies in second and a snappy aggressive pick up in all the lower gears which as far as I can see if the main joy in SD ownership. It's never going to be the fastest thing but it can the very entertainingly lively off the throttle
I have a 40 tooth sprocket just waiting to be fitted and I'm looking forward to the return of the fun factor.