Most companies offering aftermarket mass air meters recalibrate the mass air meter by lowering the voltage setting to fool the computer into thinking it's running at a lower speed than it really is. This way, the bigger injectors that you install are leaned out and the engine seems to run OK. What really happens is that the engine gets information from all its sensors (throttle position, rpm, and the MAF - even if recalibrated) and sees if they all agree. If they do not agree, the EEC believes the majority (throttle position and rpm) and ignores the minority (MAF) and actually makes decisions based on this. The result is that the timing is advanced (the computer thinks the engine is running at a higher rpm than it really is) and the result is part-throttle detonation. Many of you with re-calibrated mass air meters know what this is like. Those of you stuck with inferior recalibrated mass air meters will be pleased to know that we can partially fix your part throttle surge and ping.