Timing Issue on 1990 - 350

I am trying to check the timing on my 90 - 350. On the data plate under the hood it states to put the EST in bypass mode by disconnecting the tan with black strip wire. The wire I found under the dash hooks into a circuit board connector. Would this be the correct wire?

Im not positive but the Electronic Spark Timing control module should have a wire to disconnect under the hood back by the distributor. Can't remember for sure though.

I have a 90 K1500 truck, the wire is under the black cover on the passenger side firewall (the one that cover the power distribution block). The EST wire is black with a tan strip.

//2000CAYukon