Hi,
Are the fuel trims still the same? As far as a neg 34 STFT, that indicates the PCM is trying to cut the amount of fuel to the cylinders. Often, that is a result of a faulty fuel pressure regulator. Have you checked if the pressure is within the manufacturer's specifications? If not, that is where I would start.
Here is a link that explains in general how to check it:
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
I attached the manufacturer's fuel pressure specifications below.
Let me know what you find or if you have other questions.
Take care,
Joe
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Friday, April 5th, 2024 AT 8:46 PM