This may be crazy but here it goes any way,I have 275/60/15 bfg's on the rear of my car.Around the time i put the tire s on the car I started to get a 4th gear progressive knock if I ease into the throttle to passwith the tc locked .I did not know if the larger tires increase the load on things and maybe increase possibility of knock in any way.If I stomp it and it kicks to third it does not knock only if I gently ease into the gas and let boost slowly build it starts to move up on the knock gauge to the yellow then jumps to the red and I get 5-7 degreees of retard.I have tried fuel at three different stations and my o2s are in the high 700's to 820 when it is knocking,blm's are also fine.I have lowered boost to 15psi and fp is fine.Just taking a stab here
