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As the title says, my AFRs are reading lean (via AEM UEGO wideband gauge) showing 12+ at WOT (basic bolt on car tuned on 93 octane). I didn't have time to install my AFR gauge before getting tuned, so the weekend after my tune I went ahead and installed it only to get lean readings. Considering I was just tuned, I figured there was no way that was possible and I messed something up in my install or had a faulty sensor. Now I'm starting to question whether that's the case. So far I've done the following:

Replace AEM wideband sensor
Ensure ground wire has a clean ground
Replace fuel pump relay
Replace gasket between test pipe and stock downpipe and check for leaks (my wideband sensor is in the test pipe so I figured if there's a leak at the test pipe/downpipe connection it would lean out my AFR readings)
FPR hose is ziptied down

Something strange I've noticed is when regrounding the AFR gauge, I unplugged my battery to do so and after that I was getting normal ~11 AFR readings at WOT. After driving for a while and letting car relearn fuel trims, AFRs were eventually back in the 12s at WOT. This leads me to wonder - I installed my boost gauge a week or 2 before getting tuned and had done the same process of unplugging battery for the install. Is it possible my car had not relearned fuel trims before getting tuned and the trims didn't settle until after? I was tuned by a very reputable tuner for what it's worth.

Appreciate any insight/suggestions. I want to sort this ASAP
 

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Best bet is to ask your tuner. I don't really see an issue here. There are so many things that can affect AFR: from better gas at certain chains, octane difference, or even the temperature and humidity of the day. I'd say your WOT AFR is within tolerance. If you ain't throwing codes with that your tuner tuned you to, you're good.
 

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Yes, it could be anything from an air leak to nothing wrong. If you know what your fuel trims and corrections are, that can tell you a lot about your tune and the car itself. BTW, there is nothing necessarily wrong with mid-12s as long as it doesn't creep into mid to high 13s.
 
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