The VQ table is not associated with rpm or throttle position.
The VQ is an airflow percentage lookup based solely on maf voltage vs. percent of maximum cfm (or m3/min, m3/h, l/s, l/m, or any other volume rate of flow). This table is arranged in 64 points beginning at 0.08v and ending at 5.12v, in 0.08v increments of maf voltage output.
Values plotted at each increment are percent of airflow applied as a 16 bit number, 0-65535 decimal or 0000-FFFFhex (0 = 0% , 65535/FFFFhex = 100%), which is based off of the maximum airflow of the maf diameter as just mentioned, regardless of total hotwire capability.
Each oem maf has an element that is usually matched to the diameter so that at maximum cfm the output is near 5.12v, although this is not exactly necessary, and custom combinations, such as a 'hacked' maf, can be calibrated appropriately with full understanding and equipment (flowbench and daq). If the maximum airflow of the diameter is met before the hotwire reaches its maximum voltage of 5.12v, this will be represented as a 100% flow (65535/FFFF) much earlier in the 64 point voltage scale. If the maximum airflow of the diameter is met after the hotwire has reached its 5.12v maximum, the plotted percent of airflow will not meet a maximum 100% (65535/FFFF) before the end of the voltage scale.
In other words, the VQ does not represent actual flow numbers as a whole and that is why two completely different maf diameters (and maximum flow capabilities) will have "similar" looking values in respect to how they are used by this particular table. The main difference in airflow capability is taken care of with other global trim values (K number).
The maf voltage passes through this VQ table to obtain a percentage of flow before that percentage is used in the much larger TP calculation. The TP calculation encompasses airflow percentage, rpm, K number (global trim), temperature, acceleration of throttle position, and also o2 voltage in some applications. Airflow percentage, rpm, and K number are the main factors that are of most importance, and for the sake of this discussion overshadow the others mentioned.
The TP, or theoretical pulsewidth, is a fuel injection pulsewidth that has been calculated to provide the engine with a 14.7 A/F ratio at that particular rpm and airflow state. With all settings appropriate this pulsewidth will provide a stoich A/F ratio without any additional correction.
Now, this is where the fuel and ignition tables come into play. We all know that a stoich A/F ratio is not appropriate for all engine operating conditions, and further correction must be applied.
In the case of the fuel maps, the TP is dual purpose. Not only is this TP value applied some final correction via the fuel map value to provide the desired A/F ratio, but it is also referenced to the X axis scale (TP scale) to plot it against RPM (Y axis) to place it on this fuel correction map for a final fuel injector pulsewidth. If all values of the fuel map were set to '0', the engine would always run at stoich.
Now, to finally answer the question about the ignition timing map. Remember how the TP is referenced to an X axis scale on the fuel map in order to place it? Well, it is used in this same way for the ignition map, but instead of it being "dual-purpose", it is used only as the X axis reference. The values located on this ignition map are total timing advance degrees btdc, and after the ecu has located each value using the X axis (tp) and Y axis (rpm), the timing advance value is applied. Simple huh?
So, by altering the maf voltage via piggyback (safc, emanage) so that a different airflow percentage (VQ) is used to provide different fueling characteristics via the TP calculation, the timing map X axis reference is also directly affected. The ecu will locate/plot diffently on the ignition map, providing a different total timing advance btdc. By decreasing airflow voltage so that injector pulsewidth is less (like correcting for larger injectors), more timing advance will result due to the taper-off-as-load-increases nature of the ignition map.
In laymens terms, the ecu thinks there is less engine load, while this is usually quite the opposite (turbo app).
There is no myth to bust. This is why those who know how a piggy back works usually dont use them, and discourage others from using them as well.
Also, for those interested in more detail of the VQ and other ecu information, check out eccs.hybridka.com . There was a post where someone wanted to run nissan efi on a turbocharged lawnmower and I went into a little more detail on the specifics of the VQ.