Does anyone know what can cause a lean code to trip? I filled up with a tank of 93 the other week and the car threw a lean code. Engine sounds healthy and the turbo is putting out around 19-21 psi of boost on the current tune. Car does not idle rough. I reset the code and it hasent come back. All I/M monitors have gone to a ready state. I had the same code trip about 1 year ago and when I reset the check engine light it did not come back for some time. I'm thinking maybe a bad tank of gas was the problem. The only other possibility I can think of is maybe an intake leak.