hey everyone i'm not sure if this is the right section for this but i have a 2nd gen sunbird its a 1994 it has a 2.0L mpfi and it has the DIS ignition the car was a base model and doesn't have a stock tach in the gauge cluster. I have hooked up an aftermarket tach (2 different ones) and both times the tach was only showing about half the actual RPMs
to give you a better idea at idle they read 450 RPMs and pegging my rev limiter they read just over 3,000 RPMs
i know i hooked them up right but i need some help here

there will usually be a switch inside the tach, make sure it is set to the right number of cylinders, and if it is set to a 4 cylinder, set it to think it is a v8, and it will fix it