well being new to this site hoping someone can lend a hand on this problem.

i have a 95 lebaron 3.0 auto convert. i got it 5 years ago with 65k on it. the car was in super nice condition off a new car dealer. i took possession and on the way home the check engine light came on. i checked the codes and found code 51. we all now the code. i called the dealer to see if i could bring it back and have them check the reason the light was on they told me they sold the car as is and wanted nothing to do with it anymore. my guess is they had it in plenty of times for this problem. well in my endeavors to fix it i replaced the 02 sensor first. map sensor then egr etc. checked the vacuum for leaks using a propane torch, i don't drive this car ofter it is only a summer car on weekends to lake Michigan, i live 12 miles form it. anyway the light still bugs me and it get terrible mileage for this car 18-20 mpg.

now i have tested just about everything under the hood. took the wiring harness apart to check for bad spots ohm ed the harness to make sure the wires connected to the places needed. ran the car with vacuum lines plugged installed new injectors new gaskets on the complete engine new hoses all new sensors again 4 02 sensors. and all mopar. redid the propane again nothing is working to fix the problem. so can anyone here shed some light on this issue. I'm leaning towards a back computer. thanks. if anyone needs to see all the test numbers on the wiring i can provide it. bob p.