Fuji DVD-Rs will not burn at 16x? Upgraded...

Question

I just bought a new LG 4163B and also got some FujiFilm 16x dvd-r media. At first it would only burn at 4x. Then I upgraded the firmware from 103 to 105. Now they burn at 8x, but still can't get it to burn at 16X. why would that be? Is there anything I can do about it or try? Thanks.