There is no problem.

The Auto Meter gauge reads the signal from the stock narrow band oxygen sensor. It is only accurate in a very narrow range of operation and most of the time the ECU pays no attention to it.

There are two modes of operation for the ECU: open loop and closed loop. When it's in open loop, it basically uses rpm and MAP sensor voltage to pick a fuel value, and has a few compensation factors for things like air temperature. In closed loop, the ECU uses data from the oxygen sensor to adjust the fuel trim. This usually happens at wide open throttle or thereabouts, and it is the only time your gauge will be telling you anything useful.

As for limp mode, the ECU will only do that if there is a CEL.