This is wrong folks:

"I know what ping sounds like. If it doesn't ping at high load, low RPM, then it won't ping at high RPM, low load. That being said, if I hear/heard ping, then I would either change the gas to a higher octane, or retard the timing to an appropriate amount."

OK, not all together wrong, on a normaly asperated engine you could do this in most cases. With a *forced induction* engine things are very different. You have to take boost into account. That's the point Mr. Husky is missing. Typical SC or TC systems do not tax the engine until higher RPM's. With all the noise occuring, it is difficult to detect detonation - and often too late.
Now take a stock Xterra SC and add a smaller pulley and do it without damaging the bearings or gears in the Eaton. You've got more air(boost) than before. But what about extra fuel to go along with the air? Lean mixture = detonation. Spin the SC faster and the air from the SC is hotter too. Hotter mixture = detonation. How about the ignition advance curve? You better back down a few degrees or you guessed it, detonation.
Let me make this real clear - detonation at high RPM's with forced induction can turn an engine into a boat anchor before you can lift your foot.
Don't take my word for it, read the 'power' forums.
Think the stock ECU will magically make all the adjustments for you? Go ahead and find out. How will you know? Got a boost guage, air/fuel ratio display, SC output air temp read-out, injector duty cycle display? Then add some 87 octane gas.

dave and xtoy(87 octane), miatank(93 octane)@ 6+psi