RE: Old new car question,please see what you think
When you run a higher blend, the engine does run hotter which "cleans it out". I don't understand why it would act up switching to regular fuel. Maybe not enough additives? Sinister is right tho, run some fuel system cleaner in her. It will clean injectors, ports, and get something to clean the valves and cylinders. then next oil change, throw in some motor honey or lucas oil for max lubrication.