I think you can easier see the boost thresh-hold if you go in LogWorks to the XY Plot and plot boost over RPM. Then you don't have to put all those measurement points in.
Also another trick. If you also log compressor inlet and outlet temps you can use the LW calculator function to calculate a compressor efficiency trace. Then go to the 3D chart and plot efficiency over boost and RPM. You'll probably find some additional ponies by optimizing the boost curve for max efficiency.