Speed Control Springs problems of the 2001 Kia Motor Optima

During spring/2002 noticed hesitation of car during attempts to pass other cars on the highway. Hesitation/delay worsened over the next few weeks. It then developed hesitation after starting the car and would at times stall or suddenly "lunge" as accelerator depressed. This became a fairly common problem when starting the engine when cold. After a few minutes with the engine warmed-up it seems to run fairly well with exception of the hesitation/stalling sensation when passing. The car was returned to the dealer to fix the problem on July 18. Initially, they believed it was the computer, an air sensor or fuel delivery problem. However, kia now states the problem is a software problem linked to spring/summer gas formulation. Their solution is to make sure the car warms up several minutes before driving and that the problem will go away in the fall. Obviously, it will recur next spring. The dealership has provided us a rental car at no charge d/t the warranty. They have been exceptionally polite. Kia has been somewhat slow on their end communicating with us but polite and cordial. However, the concern remains with the problem of knowing how long to wait to warm the engine and then when you depress the accelerator adapting to the speed that is somewhat erratic. The car is often parked in parking garage and this erratic behavior represents some concern with pedestrians and other vehicles moving in a confined space.