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Old 03-18-2019, 12:19 PM   #93
Scooby Specialist
Member#: 244114
Join Date: Apr 2010
Chapter/Region: South East
Location: Louisville, KY
2016 WRX premium


I have similar fuel trim issues. They seem to crop up after the tune has time to stabilize. Around 30-60 days after running. My AF correction drops to around -35 and af learning drops to around -15. (running rich)

My tuner advised that there is a leak somewhere but I have checked every clamp, replaced the MAF extension cable multiple times, tested the MAF and MAP sensors, and smoke tested this car at two different shops with no issues found. I am running the perrin inlet with nozzle going to a grimmspeed stealth box. My tuner advised that 15+ WRXs inlet is not under vacuum like most cars, so a vac leak actually leads to a rich code. The shops are baffled at this saying that does not makes sense.

Based on this thread, I am guessing the intake and/or inlet need to come off and stock parts need to go back on. Can anyone confirm the inlet is not under vacuum?
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Last edited by sublyme; 03-19-2019 at 11:34 AM.
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