I have been researching and my problem that i have is common on these vehicles but nobody seems to find the solution. My car is a 2002 sonata 4 cylinder. The car is fine at start up, only sometimes at cold start it has a rough idle but rare. the car runs great until you put 50 miles at high mph (75). I travel at 75 mph and the car all of a sudden looses power. If i play with the gas pedal i can regain the power but its like war. If i let the car be, it will stall and after that its hard to turn back on. I did notice it only does this at high mph. if you travel long distances at 50 mph or greater i will experience this problem. anything below 50 mph there is no problem but it does have a very rough idle. So rough its hard to take off when its at a complete stop. I NEED HELP...IM STARTING TO THINK I GOT MYSELF INTO A SERIOUS PROBLEM!