Hi folks. My problem is that a digital tachometer I installed in a offroad vehicle is reading twice the rpm that it should. I am using a MSD ignition box and MSD tach adaptor. The engine is a 350 chevy with a HEI distributor. I have gone around and around with both manufactures and all the wiring should be correct and yet the problem remains. The tach has a cylinder selector switch on the back and when it is set to 4 cyl the unit reads 4x as fast 8cyl 2x. Anyway is there something I could put inline in the signal wire going to the tack to reduce the pules by half? It is supposed to be a square wave voltage signal. Thanks a lot for any help you might be able to supply.