Just had a rather interesting morning driving around with the state(qld) service manager for Subaru. We had a computer monitoring real time and logging all of the information from the ECU. He reset the ECU about half way through the drive. In my case (everyone is likely to be different)
The lumpyness through the boost range is totally down to ecu recalibrations. The ecu was retarding by as much as 6 deg. at times under hard boost! He was saying that this fluctuation of the timing ( to ensure there is no pre detonation) is what will make things a little lumpy at times. It wouold seem that the fuel quality is the stongest influence across this. I only run 98, but there can be stong differences in the quality of each tank adn the ecu takes a little time to readujust back to optimum after a bad tank. (really important not to be stupid, or duped by shonky operators into putting 91 in there, it can take months if you don't reset apparently). Anyway, it would appear that I am just being a little too picky on this front. It refused to do the bake pedal issue, or the off boost pig root witht the computer attached, so we are no further ahead with those...
Thought htis might have been of interest tho.

) I'm somewhat in the hands of the gods with ECU stuff.

