trouble shoot gas problem on a ford maverick

Was anything done prior to this occurring?
Does it stall immediately when switched over to gas?
Does feathering the accelerator keep the engine running?

There are many possible causes for the problem and they are:

1. Improper calibration.
2. Faulty control unit.
3. Gasoline not being cut off.
4. Vacuum leakages.
5. Faulty reducer.