Random voltage spikes & limp mode.

[old_man]

Unlike with a Renix era setup, there is no voltage regulator in the alternator. The alternator control (control of the voltage) comes from the computer. Replace that flakey ground strap, clean up the grounds on the dip stick bolt, and unplug, clean, and replug the ECU connectors. Look for corroded connections on the ECU and every connection you can find.