[Power Hungry]

As you've guessed, much of the changes between the low octane and high octane programs focuses on timing. There are also differences in the fuel curves, with higher octane programs being a bit more aggressive than lower octane programs. We also break down calibrations into towing and performance type programs, with each group having their own subtle changes in fuel, timing, and shifting.

The earlier 5.8L will usually gain 18-20 HP on premium (91-93 Octane) and 12-14 HP on regular (85-87 Octane). This, of course, was also 14 years ago when the engines were newer. As the engines have aged, it's going to be tough to say what the actual gains would be but I'd imagine they're still pretty close.

With everything combined, the increase in performance and economy are usually quite noticeable. Throttle response is crisper and shifting is firmer.

Hope this helps.