5.3 swap running bad hesitating PO174 code

[Ken Davis]

My truck is a 72 with a 03 DBW motor and overdrive Transmission. I got my motor running in Oct. The exhaust was installed last week. Code Po174 System to lean bank 2 came up in Dec. while I was painting the cab and frontend. Today I installed a O2 sensor and the motor runs a lot better but the code came back on. The speedo is not working (New Classic Instrument Gages)and the truck hesitates bad under accel. The truck was back firing before the O2 sensor. The fuel pressure today was fluctuating between 45 55 today it was not steady. When you step on the gas pedal the truck does not accelerate then it jumps up to the speed.