Tach connection

I'm trying to hook up a tach to set the idle speed on my 91 4d dx and not having any luck. I know I can splice into the blue wire on the distributor, but I don't want to cut wires just to set the idle speed. I've seen references to a connector either on the firewall or under the dash, but I can't find either. Where and what should I be looking for?

it is the blue wire in your gauge cluster connectors.

open ur distributer n put it in the positive side