installing aftermarket tach in 2000 corolla

I am trying to install an aftermarket tack in a 2000 corolla manual. since it uses coils instead of a distributor i was going tie the tach line of the gauge into the ECM, but the ECM isnt under the glove box. second of all i cant figure out which wire i should tie the power for the tach to so that the tach turns on with the car. the last problem is that the instructions call for the white wire to be wired into the dimmer but my dimmer has 3 wires to it and the wiring diagram that i have for the car show 2.... is there an easier way to wire the tach into the car, either striaght off the block or tie into a different wire?

If I were you I would just go to a junk yard and look for one that has the tach in it already and pull or you can ebay it online and buy one there.

I think you can tap into a wire from the OBD II connector.