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on pump gas...
NA: low 12's tailing to mid-high 11's above 6.5k or so. this is because the car is crazy knock-prone up high and you can usually make more power by richening it up a bit and keeping more timing. the rich afr's we run on these cars has nothing at all to do with an O2 sensor (the car doesn't even use the O2 sensor in open loop), it's because it buys you knock resistance, and this car is extremely knock sensitive. higher DI ratio + slightly richer than typical AFR allows you to run a lot more timing and ultimately make more power.
FI: 11.6-11.4:1, again maybe richening up a bit as you get above 6.5k... for the same reasons as above. I've found that range is a really good spot for power... still allows you to run decent timing without having to give up a bunch of power going rich. power drops off pretty hard as you get into the very low 11's or down into the 10's.
As far as what AFR is 'safe' there is no right or wrong answer. There are obvious limits: if you're running 14:1 under load NA or 13:1 under load boosted that's obviously bad... but the car can start to knock just a few tenths of a point leaner than target if it's tuned fairly aggressively. The key is just to make sure that the AFR is consistent and stays where you put it... this means minimizing fueling error to less than 2% across the board and turning off LTFT in open loop, basically. You'll never have a consistent AFR with LTFT acting in open loop and high fueling error.
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