I am also experiencing this same issue. O/D cuts out and leaves the transmission shifting hard into 2nd and 3rd gear. "System too lean" P0171 code still presenting itself even after replacing the intake manifold, manifold pressure sensor, both O2 sensors, MAF sensor, air filter, spark plugs, coil packs and a few other things I can't remember.
It used to be very intermittent, but now it happens after about 7 min of driving, every time. I keep an OBD reader, that can erase the codes temporarily while driving, that I use on longer trips. Turning off and on the car at stop lights also resets whatever is going on with the transmission.
