Quote:

...is it better to be rich or lean...



Depends on how one defines "better", & under what conditions.

No matter how your bike is tuned on the dyno, on the road the A/F ratio will fluctuate with throttle position, load, temperature, altitude, & barometric pressure.

A dyno sweep test shows you A/F basically WOT throughout the range, under a single set of conditions.

The road is much more dynamic.

The above said, I would go to the dedicated bike dyno operator. There is value to getting the testing & tuning done by an operator with substantial bike experience.

A good operator can mean the difference between money well spent, & a waste of time (or worse, BAD tuning).

The bottom line is that if your bike is in the 12 - 14 A/F range on a sweep test perfomed by a competent dyno operator then you're going to be OK.

There are folks here who can help you get there, once you have a decent baseline run & we know what your current settings are.