nah, I'm chasing a different monkey I was hoping was related to the map. Discussing it got me in this thread so I figured I'd post the book info to see if it was any help.
Appears the problem couldn't be lean/rich related because not only does the PCM not listen to the o2 sensor at WOT, thus it has no idea if it'* rich or lean, but that'* not used in determining load anyway, which by the book is the reason it would be dumping boost.
As funny as our throttle position sensors can be (and as much as people like tinkering with them), that'* probably the first place I'd look. A high TPS reading with low RPM may make the PCM think it'* under a heavy load. That situation seems to have the makings of a boost dump.
If you use your imagination a little that could also explain a bit of why changing the fuel changed the boost dump. If you were adding too much or too little fuel then you may not have been making peak power. Correcting it may have given you a few extra ponies that helped keep the RPMs more inline with the TPS sensor which would change the load reading and maybe just enough to keep it from dumping boost.
There are a few problems on the surface of that thought, but maybe something to look into. Those of you with that problem might try adjusting the TPS down a little to see if it has any effect.
Stuff got done.