Fuel Trim Reading Stuck?

[uncledave11]

Hello to everyone. got a real stumper i've been after. Recently had my 99 ES300 start running really rough (very sudden) Now after going though all the sensors, cleaning out the VVT actuators and testing of course, cleaning the VVt oil filters, removing the Idle air control and cleaning (that was sticking some), cleaning out the throttle bodies nicely....whew. now it runs and idles 99% better with just a touch of hesitation off the line. You can floor it and it goes like a scalded cat to 100! My big concern. I feel a tiny bit of mis fire (no codes) sometimes at 40-50 mph and then gone. The code reader in live mode show all the O2 sensors working within there voltage ranges but... the STFT for Bank 1 sensor 2 reads 99.2% all the time. The other two are making trim corrections but this one keeps reading 99.2% . Anyone got a clue whats going on here? Both upsteam O2 sensors were replaced about 8k ago. Help!

thanks,