Check the map sensor make sure the vacuum line is ok along with the line going to the fpr make sure its not sitting on something hot and collapsing. But dumping fuel like that and killing the fuel pump makes it run better sounds like a sticking injector imo.. pull the plugs and see which cylinder(s) are being fuel fouled, you will also be able to determine if its isolated to one cylinder or all. Stock o2 sensors usually only makes small adjustments to the fuel trims. The is quite a bit of variables still Check your coolant temp sensor and wiring, i think tsrm or somewhere on supramania has the resistances for it (same as 7m & 2jz).