I read that article and more but still fail to see how you have two different readings opposite scale.

I always believed that stft was immediate response from ecu according to what it see's from the 02 sensor and ltft was as it states longer period of correction.

So we have stft chucking buckets of fuel in (maximum corection) but ltft almost doing the exact opposite to its maximum correction. Can someone please explain this.

Adding fuel (stft +25) seems to me an air leak must exist but I'd expect ltft ro also be correcting in the same direction.

Can't you force a rich condition by disconnecting the coolant temp sensor and see how the 02 sensor reacts along with the fuel trim figures.

I still think its worth swapping front & rear 02 sensors to see if it alters fuelling.