Originally Posted by Kingtal0n

So you are saying the O2 sensor works fine. but sometimes, while cruising, it stops working, and goes full "rich" while the wideband shows a lean condition? And the engine struggles? Does the car decelerate? Does the throttle position increase to keep the rpm constant?

It sounds like the engine flips into open loop during your "condition", which would explain the sudden locking out of the fuel trim.
That could be the maf hot wire (clean it, what does the maf voltage do compared to the rest of the time? ) or an air leak between the maf and turbo (you are not getting enough air to pass the maf hotwire). It could also be a wiring issue (a sudden intermitten ground causing a sensor to fail for an instant) , a faulty tps (you would see the tps signal fluctuate, or spike).