My truck is already past th 36000 mile mark so the factory warranty in done. I do have the 6 year 100,000 powertrain warranty but I was told that that warranty would probably not cover a driveability issue like that. I took the truck to a dealer over a year ago and they said it was normal (of course but it has gotten worse) I don't understand why a higher octane almost stops it.

Your engine is pre-detonating the fuel for some reason. It sounds like its acting like a high perfomance(high compression) engine when you put the cheap gas in it. 92 octane gas is more stable at high pressure than 87 or 89, so that's shy the pinging is less noticable. I've had this same problem before also with older engines, and the high octane gas solved it. That may be what you have to do, or if the dealer is giving you the run around, I'd find somwhere else.