I would say that after about a half gallon you can pretty much go to race tune and start running the motor hard. After about a gallon it should be right at the optimal point with everything seated properly for best performance. Regarding your temp questions normal race tune would be aroun 200 to 240 degrees I would think. In certain conditions you might need to run hotter (i.e. High humidity conditions) but just remember that your engine will tell you if you are rich or if you are too lean. Just pay attention to how it runs, how it comes back down to idle and how it accelerates out of corners. All of that will pretty much tell you if your engine is tuned properly and make sure to note if the performance of your engine changes over the course of the run!