Wow, what a wierd coincidence. I haven't visited this site for a couple of years, just happened to click on the link and read this first post. I just got done resolving the EXACT same problem on my 06 a couple days ago.
According to the KIA shop manual, your problem could be an air leak, low fuel pressure, or one of many sensors could be faulty (i.e. O2, MAF, TPS, etc). Start with the simple things first. Mine turned out to be an air leak, as I found a crack in on of the folds in the intake hose. This is the rubber hose between the air filter box and the throttle body. The crack was in the flexible rubber part downstream of the MAF sensor. Dealer wants $50 for a new one, but they have to order it. Until I get around to placing the order, I just bought a roll of black Duct Tape and taped up the intake hose. I reset the CEL, and it has not returned. Maybe I don't need the replacement part after all!