4. Atomic EFI has the option to be installed as either a return or returnless style fuel system. There are many factors that need to be considered in making the decision on which way to go. Based on our location’s high ambient heat (in the desert), altitude, and the quality of California gasoline, we decided a return-style set up with a regulator was best for us. We created a new return line from the fuel line we ordered from Summit. We also mounted this neat mini cooler we got from Summit here in the framerail to further prevent hot fuel from becoming an issue.