Yes. Changing fuel quality (variable octane) is what the computer is sensing and trying to compensate for, thus throwing CEL's. One of the 3 reasons I did not want to go Toyota V8 when doing the engine swap. This may even be showing codes for the O2 sensors as well because of the erratic burn conditions. Stick with high octane and you may very well see the codes eventually clear themselves after a few consistent performance drive cycles.