Can anyone help?

I am getting a code of P1320.

What could be causing this. Some type of sensor maybe. I've had the tank scoped and the repair shop said that everything looked clear. It happens every time I get gas, not always at the same amount, but every time. Sunday I was able to put $12 in there before it started clicking.

I had the fuel line bled

Labor costs included

its a 2000 model


I have pressed the traction control button on and off, as well as the suspension "sport" mode button. Both dash lights stay lit.

Codes said to replace knock sensor but check engine light stays on.
Also, there was the smell of raw gas in the cabin and on the left side under hood but no sign of leak.

The last 4 months my car has been hesitating with check engine light on.I took it to Auto Zone and 2 codes came up to replace the air intake sensor and knock sensor. Now it doesn't happen consistently,some days are worse then others whether the car is warm or cold.Between 1500-1800 rpms the car starts chugging after 50 mph it smoothes itself out. Replaced the air intake sensor at a mechanics garage but not the knock sensor, and it is still doing the same thing but check engine light is off now. Mechanics I have spoke with said there is nothing they can do because the engine light is off. They said if its your fuel injectors you won't get a check engine light. What could be causing this?