Where is the wire that has to be disconnected set timing on a 1998 Chevy pickup?

There's no single wire you disconnect to set the timing on a 1998 Chevy pickup. These trucks use an Electronic Control Module (ECM) to control the ignition timing. You don't manually adjust the timing like you would on older, distributor-equipped vehicles.

Attempting to adjust the timing directly will likely damage the system. To adjust the timing on a 1998 Chevy pickup, you need a scan tool capable of communicating with the ECM. A qualified mechanic with the right equipment is needed to properly diagnose and adjust the ignition timing.