I disconnected the battery before installing the spacer. When finished, about an hour later, I turned the ignition on, and held the brake pedal down for a minute. And that's all. Reconnected the battery, it idled like silk, then drove it, warming it up .. when I finally hit it, it ran like a cut mouse!
Seemed to get even better over time. So the ECU was probably still 'learning'.
Make sure you don't disconnect the throttle body harness or move the throttle plate. You should not have to recalibrate it.