I recently completed an engine conversion on my 1988 RRC from the old 3.5L to a 4.6L.
In doing so, the ECU was converted to 14CUX Tornado with updated ignition coil and amplifier, with adjustable fuel pressure regulator from RPI.
The engine appears to be timed appropriately, fuel pressure is set at 40psi, the TPS is at 3.5v closed and 4.75v open, and the AFM is at 1.88, but I have a high idle, maybe 1200-1300rpm and and slight popping out of the tail pipe that isn't quite a full backfire. I backed off the timing in an effort to bring the idle RPM down and it developed an actual backfire.
The O2 sensors did have build up on them but not sure if you can clean and re-install.
Curious what else I should look at. I don't know how to check for vacuum leaks which could be a contributing factor.
Anywho, open to thoughts from more experienced people. I may have left out some details but questions will likely refresh the memory.