Tach reading 1000-1500rpm to high??

Dad n I just dropped our old factory tachs and 150 speedo off to have updated boards in them and calibrated. The guy at the shop mentioned he found trouble with Dashworx/RT Eng "updated" boards, that they would do the same thing at higher rpms. The guys we dropped ours off at said they will be "bang-on" The company we are using is Mr Heaterbox, here is their link
http://www.mrheaterbox.com/