i have a 305 TBI in a 89 RS camaro. im getting a code 43. i think this indicates a fault in the ETS system. either a Electronic spark timing module or a knock sensor bad/or connection problem. how do i determine where exactly the fault lies and what to replace. how do i test a knock sensor. they are 30 bucks, reasonable but how do i make sure thats whats bad? how do i know its not the ETS module which is 60 bucks. have any of you guys had this error and what usually corrects it. car runs great most of the time. sometimes it feels like the timming is being retarded.