System too lean...will be the death of me.

1997 Audi A4 1.8t, Had it for about 6 or 7 months, Have been getting this CEL for the past 5 Months, I have changed the intake manifold gasket, all of the vacuum lines, the MAP sensor, both o2 sensors, the gas cap. I am out of ideas. I will reset the light and after 15 or so miles it is back on. I have tried every grade of gas imaginable. Does anyone have any fresh and new idea's that I haven't already covered??

thanks

 

02 sensors? your looking at the wrong things ( air leak ) most probable

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yeah one of the o2 sensors was bad so I changed both.