Not sure if this will work or not, but for those that have not yet added a tach, this may help:

http://www.newedgeperformance.com/forractacdri.html

2003.5 MAZDASPEED Protege #1467, Ti Grey MODS: Schroth 3pt harness, clear corners, CF hood, grill, mirrors, dash, etc. Injen CAI, Defi D Boost/OilP/AFRatio, Greddy SP2 2.5" Cat Back