General Maintenance & Repairs - p0174!!!

I had my ses light come on again! Its p0174 bank 2 lean. I have changed my 02 sensor and replaced my mas! It had gone away for a month or so but its back. I have long tubes no cats. What can it be? Help please

vacuum leak somewhere on passenger side of motor.
not sure if an exhaust leak would show up as a lean condition.
but check for places air can enter into on the passenger side, including the AIR check valves.