If you're on the stock cam, then ok with 15.5 AFR - I guess. I can't run mine that lean at 35 degrees and at 55 kpa with out it lean misfiring - SS2 cam though. Mileage is important, but not important enough to lean it out to cause damage imo.Keeping it conservative until I get a spare block. I’m using the Holley, and from what I’ve seen it’s really hard to get the knock sensors tuned to a useful frequency so they’re gone. Just listen for rattle and check the plugs on occasion. Working on setting it up for lean cruise around 15.5 afr. Hopefully pick up a couple mpg.
Heads up on listening for rattle in boost - faster than your BOV can dump the boost you'll have a broken ring land or windowed block. Tuning timing by ear is not a motor life increasing plan.
I've leaned hard on stuff that gets daily driven and it's been a money waste. A spare motor is good thing when they can be had for $250-300, but having one is not a good reason to find the limit of yours. If yours works good, then I see no need to not be conservative for a street tune. And that goes double if you have a Gen 3 setup. You're probably in the 500+ whp range. On the street you'll find little no difference between 500 and 600 - again IMO.