The phenomenon you are describing sounds to me like you may be entering PE. I would take a look at the log and see if that flag or another modifier is enabled. From observation of my own logs when you enter PE mode it effectively ignores the fuel trim and locks the BLM at 128. IIRC some people will actually tune out PE (set the temperature or TPS to enter at an extremely high value) to tune some of the heavier load parts of the table because the tendency of the ECU to want to enter PE when under high load.

If this is happening you can actually have sections of your fueling table (roughly from 75-100kPa) that will be completely wrong but will be "hidden" in the history average in TunerPro because it doesn't filter data. This is a problem I have with the classic method of BLM tuning these ECUs using that history average. If you disable PE this average would look closer to the filtered data you get from other means. This is an advantage of the sheet from dave and also the software from steveo as both of there methods filter the data so that the averages only include data from points where PE is inactive if I am not mistaken.

Just my $.02