When you do the registry hack, the PIE reported by CDSpeed on the Pioneer are eight times the "normal" PIE values.
So "max" PIE then reads as 8 x 280 = 2240.
PIF values seem to be consistent (max 4). Not 100% sure though. As long as there is no official support, we are rather in the dark.
Indeed the Pioneer is not a good scanner, but if you want to compare different medias on the 109, you may give it a go. But you won't be able to compare your results with the ones that others get with CDspeed on other burners.