fast efi problem

Sounds to me like you have a low voltage problem to the fuel pump. WOT like at the track is ok. Running around town and slow cruise brings low voltage. Is your alternator or voltage regulator on its way out? Check your Fuel Pump wiring too. With the 00 on o2 sensor would make me think it's going way past lean to not even register on the gauge and stalls out.

What fuel pump are you running?