I have experienced the same problem as alexnoe.
Burning a 50 batch of TDK -R 8x@8x (TTH01) and a 50 batch of TDK -R 8x@8x (TTG02) without any issue having Powerec ON.
Now I got a batch of TDK +R 8x (TDK-002-00) burned @8x PR ON.
My scans could be a copy of alexnoe's scan.
There is a drop in the read speed curve even reading with my PX716.
My Toshiba has problems at this place too, but can read it with reduced speed.
Only reading with the PX116 shows nothing special and has a smooth reading curve.
The read speed drop is exact at the place where the Beta makes a big jump.
However with Powerec OFF I have no issues at all.
In both cases (Powerec ON and Powerec OFF) SUM8 < 25 and SUM1 < 4.
Powerec seems to do something strange changing its writing strategy while increasing the write speed.
The conclusion: Powerec must be definitely switched off using this kind (or batch?) of media.