Flashed 5007 too, for me PBO seems to ignore negative voltage offset. Voltage always goes to 1.38 when running CB20, no matter what I have, from auto to negative offset with -0.10 (also tried -0.05 and -0.075). Without negative offset, PBO is unusable for me, there's no point going to 1.38 for 4050-4075 on CB20. Boost starts from 4150 (+200 over 3950 when PBO is disabled) but with so high voltage, it immediately drops down to 4075 or 4050 due to temps going 70+.
I also still have a screen with a cursor in top-left corner for 1-2 seconds when booting (before the ASUS logo is displayed). This appeared on 4804, I never had it before. I went from 4204 to 4804 and now to 5007.