Alright I'm at the end of my wits. I have a gen 1 Busa engine in my sand car. I'm getting the C24 and C27 codes. (Ignition signal 1 and 4). I ran a NA motor in the car for 12 years. Lost the bottom end. Picked up a new motor and Turbo. Original block was a 2004. New one is 2001. I'm using the same ECU and wiring harness I've run for 12 years. Never had any electrical issues before. Now I have these codes. Engine will start and runs fine with no load. Under load it falls flat over 6000 rpm. Can't build boost. I have a shop manual, I've done the troubleshooting. Swapped the Coils around, Tried other coils, Tried another Cam sensor, Tried starting it and unplugging the cam sensor, Tried 3 different CKP sensors, Gone through entire wiring harness, Checked voltage and resistance everywhere. All looks good. Only thing I haven't done is try another ECU because I don't have one. I do run a PC5 but still gets codes without it. I've removed the boost and still codes. Can't shake these codes. Driving me crazy. I've missed an entire dune season chasing this issue. Any ideas? I have read somewhere about getting the ECU flashed can remove codes C24 and C27, Wondering why the Flash would do this? Why? Would this work in my situation? Or do I risk hurting something?