I need some help here. The fuel pump on my 96 Tahoe recently went out so I replaced that with a new one from Carquest. Immediately after I changed the pump I got a SES warning. I pulled the Neg. cable to reset the system thinking it was just from replacing the pump. The SES came back on so I went to Advance Auto to find out what the error was. I have two errors, both are for Rich Fuel on both banks. They had no idea what could be causing it. He reset the SES and it came back on after driving for about 10 miles. I talked with a mechanic friend and he seemed to be at a lose too! I don't want to start changing O2 sensors or Mass Air Flow sensors if I don't need to! Thanks for the help!

What this means is too much fuel or not enough oxygen is being dumped into the compustion chamber.
Could be caused by excessive fuel pressure from the new pump (may be wrong pump for the truck)
Since this started after you replaced the pump, I would check fuel pressure first.

The fuel pump is an exact replacement of the fuel pump that went bad. Both came from Carquest. Is it possible that the Mass Air Sensor was bad before the new fuel pump but there was no error because I wasn't getting enough fuel before. Now that I am getting the proper fuel volume the lack of oxygen is evident?

I have verified that the fuel pump is the correct one and the fuel pressure is also correct. Is the next thing to try replacing the Mass Air Flow Sensor? The truck runs fine except that it seems to have reduced fuel economy and the engine light stays on for the rich fuel error. Any advice??