From the factory, these cars run a little fat all around. The thing is, unless you have a before and after of each run of your own car, you won't know what to set your particular vehicle to. Even the same wideband O2 can get different readings on the same car depending on where in the exhaust you're getting the readings, let alone two different O2's on different cars, on different dynos, from halfway across the country. All said, aim for the safe side of stoich, then lean out to where the vehicle stops responding and back it off a bit.
