2008 H2 rough idle

[Little General]

Anyone with an 08 noticed the idle being rough. Mine idles around 500rpm and the dealer says it should be 750. They said they have not had any complaints but I found a Hummer forum that had a thread about it. Now I can't find it again. I asked about a reflash but again it seems I know more about Hummers than they do, the answer was no reflash as of yet. Of course they asked me if I was using 93 octane and I have since new. Then the salesman who sold me mine says they fill all new ones with regular, it cost too much to buy premium. Duhuh...for $70,000 you would think they could buy 93 . Plus this is the first new car I have ever bought that the first oil change was not included; also, being the "corvette" engine it didn't even have synethic oil . Now mine has Mobil 1 in it.