are you putting an aftermarket in?

there are quite a few spots you can tap in:
1. even if you're tachless the wire is in the harness plugged into the cluster. remove it and tap there.
2. at the ecu. find the tach wire and tap there.
3. at the firewall on driverside there is a wire in a rubber boot not connected for a tach signal.

i used the wire behind the cluster so i didn't have to push one through the firewall and my wideband controller get's one at the ecu. seemed easier to me than going into the engine bay.