Just replaced the ignition system with a MSD 6A, and Accel Performance dist. I have it hooked up like a magnetic pickup. (Had to take the module out to get it to work). The SunPro Tach used to be pretty accurate, but now isn't even close to the right rpms. What did I do? Thanks Kevin

I think you need to get the adapter. Look in the directions,there is a chart, it will show the part numbers of what tachs need it and what ones don't.