You have the 2 white plastic connectors used with the OE 4 terminal "dual" ballast/5 pin ECU setup? You want to use a "single" 2 terminal ballast with an FBO 4 pin ECU? Correct so far? Plug the "single" 2 terminal FBO ballast into the sides on each connector half that has the brown/blue on one end. Another option is to keep the OE "dual" 4 terminal ballast & jump across the brown/blue and the green/red wire terminals just like the other end is OE jumped with a blue loop. this will give a parallel circuit across the ballast & in my case it gave me 1.1 ohms (the auxiliary side had 6 ohms and the coil side had 1.6 ohms). You can also use 2 "single" 2 terminal ballasts side by side in the "dual" ballast double connector to get the ohms you want either keeping one of them unconnected for a better appearance since there is no unused terminals or parallel wiring them as the width of 2 "singles" is the same as a "dual" & will fit the 2 white "dual" connectors. You have ALOT of leeway on how much or little ballast you can get by with. Always carry spares!