I am almost a complete noob with tuning but I did learn one thing that I thought I would share and maybe help others. I have an LHU in a standalone configuration and over the winter I carefully rewired it to get rid of the rats nest. In the process I changed the ECM main power from a high quality toggle switch to just a regular ignition switch, and DTC codes P0603 and P0686 started popping up. I changed to a 30 amp relay to send power to the ECM and getting no more codes and the car starts and runs noticeably better.
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