On my original cvh setup with sierra clocks the rev counter wouldnt work from the megajolt or edis and would only read approx half or less
You buy a tacho driver from trigger wheels and run it from the coilpack and that sorts it
As tt said though may not need it depending on dash, but i did
So just be aware of this when you have the rev counter wired up that it may be under reading whilst your revving the tits off it thinking this is loud for 3500rpm
