Hi and Lo Det fuel maps seem to be unique to this ECU and are not present as far as I know in the later 2001> ECU.
On the later ECU normally there is a Primary Fuel Map and a Failsafe Fuel Map, plus Base Ignition Timing and Ignition Advance.
Which map gets used is mainly determined by Knock readings and the Ignition Advance multiplier trigger point. For example if the IAT drops to 4 the Advance Map drops the amount of timing as I described in an earlier post. In some cases it may switch fuel maps. This just provides a safety backup of giving extra base fuelling, so does not need to be considered greatly other than alignment of the load scale to ensure the ECU still has control under these Failsafe conditions. Many pro tuners may not even touch this during their 15 minute dyno tune.
Some XML definitions list a Fuel Map A and Fuel Map B which appear to have the same values. It's not understood as to when A or B are used, so the guidance is to make the same changes to both.
With regard to the MY99/00 the hi and lo det fuel compensation maps have been converted believing they represent an AFR correction value, which is most likely dependant on knock feedback.
However, as with alot of the maps and parameters available to adjust there are many than can remain untouched.
Treat them as tools that apply an operating tolerance to the tune.
If when tuning you are setting the key maps to operate within your requirements then these 'tolerance' control maps can be left alone.
This not only applies to the Fuel/Ignition but also the boost control.
On the later ECU (I've not yet found def's for MY99/00) there are also Turbo Dynamic control maps, which again help by applying an operating tolerance and fine tuning.
But as long as you have your Max and Min Wastegate % set to achieve your desired target boot, with very little under or over achievement, then the Turbo Dynamic parameters don't need to be touched.
These fine tuning maps were obviously setup by the original developers, so I figure that as they had much wider knowledge of the ECU operational code, then they are best placed to decide how wide the tolerance needs to be to maintain good and smooth control, of the key operational settings.
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