I got a new Digatron gauge w/all the bells and whistles, and when downloading all the info on the computer, it shows the rpms, etc, and when my tach showed the peak at 8,900rpms, the recall on the gauge said it hit 8,850. At those speeds, 8,900 and 8,850 sort of look the same. I think on the top end, the tach ran pretty true. Never really investigated the lower rpms, but probably not too far off.