It IS strange. I've never even tried the 93 octane tune though. Since the engine is really a low-compression engine, it seemed to me like I'd just be wasting money putting the anti-knock juice in it.
About the tire balance though, I think that is a "real" issue. (And I know it's not YOUR issue because tire imbalance is very predictable and ALWAYS happens at certain speeds). I've had the tires on my truck balanced four times already in about 20,000 miles. The last time they were unbalanced it was right after they had been rotated, nothing else, no thrown weights or anything like that.
Somewhere, back when I got this truck in 2007, I read quite a number of reports of it being very hard to keep an imbalance vibration out of these trucks. I think there's something a bit flaky in the suspension.
Bill may have some thoughts about the 93 octane tune and your symptoms though if you really wanted to use it. Glad you like your custom 87 octane tunes though. I really don't see the need for more than two tunes actually, one for towing and one when I'm not. AND, if I'm off on a trip with the trailer, I just leave the tow tune on all the time. The last thing I want to have is a programming failure in the middle of nowhere.
- Jack