Multi Map Selector, Engine Control Module Selector Switch, For Use With Holley Dominator EFI. They allow up to four different calibrations to be selected at vehicle key-on. The included switch is connected into the J3 ECU connector. Multiple maps can be used for many different purposes, such as various fuel types or octanes; charting track conditions, nitrous setups, and more.
558-407 Dominator EFI Multi Map Selector