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My car is tune by Petey at PA. Blot on with MHI 18K turbo, making 406 whp on 93 gas. The car runs great for the past year. But this few month, my car is misfire at 6500 rpm every gear. I have change spark plug and coil pack. the car runs fine again. But however, Whenever I boost my car, my air fuel ratio is between 12 - 12.8. It is running lean. The car was runing 11.4 - 11.9 before. can someone please help me with this. no light, no error. just the AFR is reading high.
 

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Ask your tuner! He is the best one to ask, since you can him log. He can look to see exactly what is happening.

I have nothing to suggest apart from exhaust leak somewhere

Sent from my SM-G950U using Tapatalk
 

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Yep, get a log and send it to your tuner. Your safest bet is to work with him.
 

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Are your AFR readings normal at idle?

Logs should be telling... you could have developed fuel delivery issues (weak pump, o-ring blowout, etc)

Exhaust leaks upstream of your UEGO can cause bad readings too. Sensors are also fragile and not the longest-lived. Depending on your gauge you might need to recalibrate. You might also consider getting a fresh one.
 

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Also, obligatory, the FPR hose can sometimes pop off the intake.
And finally, the fuel pump relay sometimes is the cause.
 

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14.7 and 15.2 is fine. It always moves back and forth, as long as it's roughly around 14.7 is what you want.
 

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Idle runs normal i believe, but sometime keep going between 14.7 - 15.2. how can i recalibrate my gauge. Is AEM Electronics Original Wideband O2 UEGO.
UEGO does not require a free air calibration.

If you never replaced your exhaust manifold, it could be the cause of the lean issues. The stock manifolds are known to crack over time and cause issues.
 
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