Hello Im Bryan I will try and answer your question.
Mass air flow sensor can cause this problem, but unlikely
This could either be a transmission related issue or a engine issue
Does the vehicle hesitate or act as there is a misfire at the speed you mentioned?
Does the vehicle hit a specific RPM range where this occurs and can you get this issue to happen with the vehicle parked.
This could be caused by clogged catalytic converters or from a fuel pump going out I need some more information to answer your question.
This sounds like a mass air flow sensor or a fuel pump, to determine which one, I would purchase a can of Mass air flow cleaner and spray your mass air flow sensor and then asap test drive the vehicle. If no change is seen I would be looking at the fuel pump.
If your mechanic has a scan tool that can look at live data when this is happening have him check the PID blocks for fuel trim if the vehicle goes rich the problem is not in the fuel pump its in the mass air flow sensor, if the vehicle goes lean it could be either the mass air flow sensor or the fuel pump. But like I said this sounds like a mass air flow sensor.
Being the fuel pump was recently replaced I do have one question was the fuel filter replaced with it. a clogged fuel filter can cause this issue also
I would try cleaning the mass air flow sensor which is easy
just remove the air filter box spray the cleaner on the sensor and reinstall then test drive vehicle asap and see if problems is gone if is then replace the mass air flow sensor
Testing with a used sensor is useless his sensor could be just as bad as yours.
With the vehicle on but the engine off press the gas pedal to the floor for 1 min this reset all adaptations.
Clean mass air flow sensor and replace air filter if needed
Next yes replace fuel filter if problem still present
last would be having the vehicle diagnosed for either bad mass air flow or bad fuel pump
this is not that hard with a scan tool you can read the computer and see what the mass air flow is reporting if it is reading 100kgh then drops to 40 when the problem occurs there is your issue.
Other than that a fuel pressure test will tell you if your pump and filter are working correctly
I believe so
The crankcase gasket is confusing Im not sure which gasket they are refrerring to but if its leaking air into the crankcase the result will be the engine runs lean
Lean makes more power but if to much air gets in the engine will misfire and the vehicle will seem sluggish