Yeah, I sent a number of emails to Chris at KaganTuned - he's a really nice guy and gave me a ton of details about his tune. He seems to be more aggressive with timing and fuel control than others. Case in point, he's running his engine pretty lean at 12:1 AFR's on the current tune (93 octane), with plans to lean it down to 12.4:1. Up until now, most tuners have kept things richer than 12:1, for concerns of potential knock and running too hot.
I don't know where the line is in terms of what AFR is safe in our engines; but, most DI engines allow leaner running conditions compared to their port injected counterparts.
I'm planning on leaning my car out to 12:1 and checking on the
plugs after a couple thousand miles and see how it looks. I assume it will be fine, since my AFR's with the JB4 are 11.8:1 already, so it's not a big difference, but it really seems like we make more power having it run a little leaner. But, again, the question still remains: how lean is too lean?