Can anyone help. I have a 95 LT1 and DTC 18 is setting. It makes the engine run slightly rough and it is making DTC 55 set. 18 is Injector Circuits, and 55 is fuel lean. 18 is forcing the motor to run lean. I have checked the injector harness with noid lights and everything checked out ok. The injectors physically look clean when taken out, and ohm test places every injector within .2ohms from each other. Any common issues I should know about?