I had the same issue, on cold start rough idle and while the engine was still not up to operating temp very uneven acceleration, even occasional loss of power during normal driving. You definitely have a problem with your fuel pump. Get it replaced - the high pressure fuel pump in the engine - Direct Injection fuel injectors operate at ridiculously high pressures 2-3000 psi so the high pressure fuel pump is critical. Also, ask about the ECU, I would think yours is still a fairly early build that would warrant an ECU replacement. If it's not easy working with your dealer, change dealers or call Kia directly.
