7 The days of carburetor adjustment and tweaking are over. Here’s the Holley Avenger EFI Engine Management System (ECU) and hand-held programmer. You can locate the ECU just about anywhere. We suggest locating it away from heat, moisture, and road dust for optimum performance. You can locate the ECU inside the cabin underdash (which mandates boring a hole for harness passage) or locate it in a safe place underhood.