Something you ought to do is run the fuel down pretty low and then refill with the fuel you intend to use.
Then, reprogram the PCM. Then disconnect the battery. Then turn on/off the headlights and reconnect the battery. This will reset everything including tranny functions.
Then.. let it relearn the idle functions (search under my recent posts on how to do it)
Your on the right track. Run what every fuel you want and then play with the tune to get it to not ping. *Then* back it off another 2 degrees of timing.
Also, if you have a laptop you can hook up to the X-CAL 2 and the pcm and data log. Having the laptop beside you on the seat lets you see live what timing your actually running.
He who is enslaved to the compass is free to sail the seas