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.