I heard that there was a computer thing they run through the car's ECU and it clears up the problem of jerking when the car is cold. I think it is an ECU update. If you guys did do this, how much did it cost you?

I went to the dealership and I asked them and the service guy said that he knew what I was talking about. But then he said that it would cost $120 just to diagnose the problem and he had no idea what it would cost to fix it. I have done this all before about a few years ago. It never got fixed and I really don't want to pay $1,000,000 for it to not work again.
Is there a name for this updated upgrade?