I completed the same mod and have experienced similar results.
I used an AEM inline controller (P/N 30-0310) and used the existing 02 heater and ground circuits on the harness to power the controller and ground the sensor, respectively. Reduced overall wiring and seemed neater.
The controller cycles power when a WOT condition triggers the heater relay, but I’ve found it to reliably start swinging again before the ECU reverts to closed loop.