Just closing the loop on this thread -- I finally got the ProCal tune loaded last week, and I'm very pleased. Throttle response is better, and the car pulls stronger, with no detectable knock so far. I'm using 93 octane Chevron fuel. Ford Racing originally sent a defective tuner, which was disappointing because I specifically requested a new, rather than remanufactured unit. They shipped a new one overnight directly to the dealer, so it wasn't a real big deal -- but did require an extra trip in Atlanta traffic to get there! My service rep on the 2nd visit was a former Steeda employee who is on this board -- super knowledgeable about tuning, and very helpful!
I'd also like to thank the ProCal users who chipped in on this thread, and helped me make the decision to go that route. I'm not planning any further engine/exhaust mods, so the ProCal tune is fine!