How did you get the performance you cite?

I have a DVR-110D and a DVR-112D. Both drives burn DVD+R at a maximum of between 2X and 3X.

System:
Intel D975XBX2, P4 Dual Core 3GHz, 2GB memory
Boot & Data partitions on 3Ware 9650 true hardware SATA2 (3Gb/s) RAID-1

I have done all the research and found the articles on various sites about making sure the IDE controller is in DMA mode instead of PIO, and also done the ResetErrorCountersOnSuccess=1 workaround in case that was the problem (but no errors are being recorded in the event log). Both drives show they're in UDMA-4 mode, which is what they should be according to Pioneer's support docs, and this is supported by examining the registry.

I've deleted both the drives AND the IDE controller in Device Manager and let Windows reinstall them at reboot, but this didn't fix anything. I've even swapped the two drives' positions on the IDE cable (with appropriate master/slave jumper changes) with no effect.

I'm at a dead end. The only remaining possibility is media: I'm using Memorex 16X DVD+R. Anybody have experience with the combination of Pioneer drives and Memorex media?