Plugs 1 and 4 run off the same coil. I think the coil is bad not the FI. The first test is to lay all four plugs, connected to their respective wires, on the valve cover. Crank the engine a few seconds while observing the plug ends. Probably only numbers 2 and 3 are sparking. Since the coils ain't cheap, as a final test, switch the coils. If numbers 1 and 4 now spark, but 2 and 3 don't, you need a new coil.