Running Problems

I have installed a 4.0L from a 96 XJ into my 86 CJ. (Its OK, I own 2 XJs also, no jokes please) It seems to run good with plenty of power but has a problem with a miss at all RPM's. The computer code (p0171) says it is sensing a lean mixture and is overcompensating and running rich. I have checked and cannot find any vacuum leaks. I have changed the fuel rail and installed new o rings. I also had a shop check and they couldn't find anything. I have swapped all the sensors (TPS, O2, MAP, Idle solenoid) with no difference. I am using an aftermarket Pressure Regulator and am getting the proper 49 PSI.
The other code I get is (76?) which is overvoltage. I know the computer controls the voltage regulation. The voltage measures 14.8 volts. Could there be some link here?
I am at a loss, anyone have any ideas? I appreciate any help you might give.

Does the 96XJ use one or two O2 sensors ? I know 97+ uses two, one on the downpipe and one by the cat for downstream. I'm not sure of the relationship between the two or what effect not having the second one would be. Also what about your grounds ? got enough of them and are they all clean ? Might consider running a few heavier ones between the engine > frame, engine > firewall, engine > battery.

It uses 2. The downstream one, behind the cat, compares to the upstream one to check the cat is working properly. I have swapped those out and tried a few other things with them. Most of all the grounds are at least 10 ga other than the engine to chassis and engine to body which is braided cable.