I have run WI at an AFR of 10.8:1, basically at a rate of %14 to fuel flow. Operation was fine @ power level of 472 rwhp.
I use a very strong CDI ingintion set up which I found mandatory when using WI at this AFR.
I have used AFR's of around 13.7:1 !!! with 20psi boost pressure on normal 98 octane (RON rating) again with WI at a simlar flow rate percentage to fuel flow.
All good results