In most non SFI OEM MPFI applications from GM, the ECM only had one injector driver. The only exception I can think of is the Turbo Sunbird, Turbo Grand Am, Sy/Ty and a Quad 4 application (Beretta?), that used the '7749, that has two injector drivers, but in saturated mode (Sy/Ty for sure), only one driver was used. in Peak and Hold mode (Sunbird and Grand Am), both injector drivers were used.