Hi Pinknoise. A few months ago I updated my Sony DW26a to the equivalent liteon firmware (it was equiv to the litey sohw 1673s). Despite being supposedly an "identical rebadge" for some reason it just never burnt very well with the liteon firmware. I tried several versions of the liteon firmware but all gave me poor results. I even tried "resetting learnt media" etc but nothing helped. Eventually I switched back to the official Sony firmware, the drive just worked better with it.
Don't ask me what/why because I don't know, but something must have been different on that Sony compared to the so called equivalent liteon, because the liteon firmware just didn't work so well on it.
My advise would be to try the utility to reset learnt media first (and burn a few DVD's after that to let it settle in), but if it's still inferior then do what I did and just go back to the Sony firmware.