vehicle hesitates between 35 to 45 miles per hour

Vehicle hesitates between 35 to 45 miles per hour and at times it lounges forward almost hit a school bus last winter. Keep taking vehicle to Hyundai and they keep telling me that they CANNOT duplicate the problem. I had this vehicle in the shop including this coming Wednesday this will be number 5 going to the shop.

I am very irritated and upset that they cannot find the problem when other people are having the same issue, kinda makes you wonder if they are waiting for your warranty to expire!

While driving after just slowing some, like making a turn, would set on the gas but the only action would be the tach almost red lines. The shifter is in drive, the dash light shows drive but the car is just coasting. After few hundred feet most times and several steps on the gas the car jumps forward and drives ok.That is so far been lucky no car was in front of me, more worried about the guy blowing his horn behind me. There is no warning before or after, no noises. Some days this happens 3-4 times then ok for months. Been living with this same problem for five years. Multiple trips to the Hyundai with this complaint. Told the same thing each time, We ran the computer check and showed nothing, come back next time you have this problem! I surprised them two weeks ago, complained again but this time the computer showed [ system ESC] DTC C1604 ECU Hardware Error. Second page of the printout says possible Faulty HECU. The service tech said the ECU is expensive[ what is cheap anymore!] Since that part is not part of the power train and having this problem for five years gave them a guilt free excuse. BUT I had bought a extended warranty when the car was 3 years old[ good for 4 years, expires this year in 2 months. They called the Carefree Car Protection [had paid1569.90] for this protection. Next day this co service person checked the computer report and decided to clear all history from my computer, drove my car around the dealers parking lot, rechecked the computer and everything was ok. After five years complaining and checking finally the first and only code that pops up controls when a transmission changes gears, [ told that by the service tech] I made this a long story because there are 4-5 other with the same unsolved complaint. Hopes this helps someone. DOT has complete all doc's sent last week.