Jim Lill writes; Carter used to make a box that was an aftermarket add-on. It used a common microphone/sensor for all # of cyclinder and had a 4/6/8 switch. -------------- I used to have one and it DID work well. Until the car wouldn't start one day and I disconnected it. Aftermarket stuff just wasn't robust in the 70's and 80's IMO. But it did do the job! bw