Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › mt2500 › mt2500 January 2, 2020 at 11:03 pm #895640 college manModerator There are know real fuel trim charts. What we like to see is 10% positive to 10% negative. The readings may spike to 25% either direction. But the more the 20-25% range is held there you will set a code.