Please help with these codes

[pearce trucking]

2791 would be the egr valve actuator that opens and closes the valve. May be a sticking valve that doesn't automatically return to its closed position like it should due to soot or other contaminants.

412 is the sensor on the pipe between the egr valve and the delta p tubes. if its bad it could cause the other problem. assuming you have a cm871 of course.

Others may correct me but this is what I think it is.