Hi There

This is my first post so i hope someone has come across this problem before and can help me out,this is a factory fitted lpg astra that has a misfire after checking everything i have now found no 1 injector is not working and have changed it with another that i knew worked and still no joy i did do a wire test and there is no breaks that i can see so is it the fuel ecu playing up? the injector wire runs into a black box next to the fuel ecu i have no idea what this does so also can someone throw some light on this too i,ll await any answers.

Thanks