1995 Jeep Cherokee Country fuel injection problem??

I have a 1995 Jeep Cherokee Country 4.0 Automatic. It has drivability issues and a check engine light reading 'fuel injection circuit' with the onboard diagnostics. This vehicle is OBD 1 system. I have replaced all 6 injectors, fuel pump, fuel pressure regulator, fuel filter, muffler, exhaust, catalytic converter, oxygen sensor, cleaned the throttle body, replaced the ECU, and the wiring harness for the injectors. Help please!!! It just acts as if the vehicle is not firing on all cylinders, and this is an intermittent problem. Some times it will run alright, but most of the time the check engine light will turn on and the vehicle will be running rough. I have had it into two different garages and they can't seem to fix the problem. Thank you!!!