Hi dashman, welcome to the forum!
In order for your 16x media to be compatible (i.e. offer relevant burn speeds up to 8x), it must be included in the drive’s firmware. You can check the supported MID (Media or Manufacturer ID)-codes in MS0R with OmniPatcher. At first glance, I don’t see any 16x media listed in there (even 8x support isn’t complete).
You can always “import” your 16x discs’ MID into the firmware with OmniPatcher (just overwrite an unused MID) and then try to burn it with the equivalent 8x MID strategy (or any other strategy for that matter, but this might be your first choice). For example, import MCC004 (16x Verbatim) and assign it the MCC003 (8x Verbatim) strategy.
This is if you want to get into it, the safer and less involved options would be buying 8x rated media or buying a new burner, as already suggested.