Per the UltraGauge manual:
Quote:
"Fuel trim refers to the fine tune control of fuel delivery and specifically indicates adjustments made dynamically to the base fuel table to obtain the proper ratio of fuel to air. The fuel-to-air ratio is adjusted by increasing or decreasing the time fuel injectors are open. Note that fuel injectors are either fully open or fully closed – there is no variable opening.
…Fuel trims are expressed in percentages with a range of -100% to 99.2% of nominal. Positive values indicate a lean condition exists and the injector is left open longer to compensate, thus adding more fuel. Negative values indicate a rich condition exists and the injectors are closed more quickly thus reducing the amount of fuel."
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I don't think you have a problem at all. Your car has a table to know how much fuel to supply. The value is just a percentage difference from the value on the table. According to the second paragraph, the ECU is doing exactly what it should be doing. Your WAI is creating a rich condition, so it is scaling back the fuel injection (closing the injector sooner). This results in a negative value on your UltraGauge.
From the details you've provided, it seems like everything is working perfectly. How's your MPG at the pump?