OL-fault means its in open loop because it has detected a fault with one or more parts of the closed loop system. O2 sensors being the most common. O2 sensor wiring harness issues. MAF sensor problem or vacuum leaks. Then fuel pump/ fuel pump voltage control. Leaky or clogged injectors. Clogged fuel filter.
The way you describe it, it is normal for the car to be in CL when less than 50% throttle, and switch to OL at 50% TPS or what ever your OL TPS threshold is set to. I dont think it will say OL-fault, just OL or OL-Power enrichment. There are other thresholds that can make it go into OL as well. In order to target the richer lambda than 1, it needs to ignore the narrow band sensor corrections and run in open loop. This is why a wide band sensor is needed to tune that area, because you can't see what the lambda is with the narrow bands. Its perfectly fine to set up a tune to run open loop 100% of the time. It does makes tuning a simple setup like CAI and Headers more difficult. It isn't something that you normally need to do, and if there is a problem its best to find and correct that, than calibrate around it.
Setting the car to run CL all the time, will make it run lambda 1 at WOT, and that can be very dangerous for the engine.
These three changes, some on the axis values, will help it stay in CL longer. I would not advise extended periods of WOT with out PE(10 seconds or longer), or going any more aggressive. Give it lots of cool down time between pulls, don't just pay attention to ECT as thats not the full story of temperature of metals/components inside the cylinder, give it a few minutes or miles of normal driving for heat to dissipate.
stay in CL longer.PNG
Maybe even target .82-.83 to make sure its adding more fuel than needed until you know for certain the wideband is reading where you want it, and you can put it back to .85-.86.