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Well...... actually, and I'm saying this to help, you're backwards. Timing is advanced with rpm, the mixture burns at a fairly steady rate so it needs to begin earlier to stay ahead of the increasing piston speed. So... Timing will advance normally and if the knock sensor(s) detect pre-ignition (detonation) the computer will gradually retard the timing. No knock, no retard. The 12-28° advance limit is in addition to the base timing.
An added benefit to reducing oxides of nitrogen through the EGR system is that the introduction of an inert gas into the mixture reduces flame propagation speed and results in knock reduction also.
Your timing measurement is right on and doesn't indicate any problems. Next thing I would try is disconnecting the MAF and see how that affects the problem (disconnect with key OFF, then restart.)
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ASE Certified Master Automotive Technician w/L1.
ASE Certified Master Medium/Heavy Truck Technician.
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