While driving my 94 V-6 probe, power was lost. Battery replaced.
Worked for 1/2 hour then began losing power and fuel cut off light came on.
What is wrong?

I would suggest you charge up the battery. Then use a DVOM and make sure your alternator is charging properly.
Advance and Auto Zone while check your system free.

fuel cut off light came on

This is a classic symptom of a bad alternator.