I too have the hacked 1.13 firmware and Nero 18.104.22.168 and I have a Pioneer 107D that burns Ritek-G04 at 6x or 8x flawlessly.
However some RiteK-G03 simply refuses to burn at 2x. Just burns a little bit and out pops the disk with write errors. If I set it to burn at 6x, it burns okay, but the burn quality is bad.
Maybe I have a bad batch of those Ritek-G03 disks. Will try my old stock of TDK and Fuji and hopefully they will burn fine.