When driving 40MPH to 50MPH, my car starts to stall

Hello, there can be quite a few components that can cause these types of issues. Does this happen every single time you reach 40-50MPH, each time you drive the car? And does it happen after a certain amount of time driving and does it make a difference if it is colder or warmer outside? It doesn't sound like an ECM problem, it sounds more like a sensor failing, a fuel volume issue, a failing catalytic converter (when the problem happens pull over and see if the converter is glowing red hot under the car).
Does the problem go away under a certain MPH, or do you have to pull over and restart it? When was the last time the car was tuned up? And any other details you can give will help. Has the check engine light come on at any time? Even if it went back off, there can still be a code stored.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

https://www.2carpros.com/articles/symptoms-of-low-engine-power