I can't say I blame you. Bear in mind though that nobody has figured out yet how those OEM models end up on sale on the market. It is either LG releasing it or computer manufacturers selling their surplus stock of drives left after systems are assembled (which they should not do because they know the drives will have no firmware support).
Either way it sucks because you the consumer suffer. It's a darn shame. I only wish you could have asked around here before getting it.
Alright, it is clear enough that the burns are obviously bad.
I don't think you can. I have only been able to find 1.05 for the GWA-4164B (not from TDB). In any case, you already cross flashed the drive to a 4166B so I am betting that the GWA-4164B firmware will refuse to flash your drive, claiming it is the wrong model.
There is one thing you can try though : here is a link for firmware 1.01 for the GSA-4166B. It is slightly different from normal GSA-4166B firmware because this did not come from LG. Try it and see if it fixes things :
If 1.01 doesn't work, you can try 1.00 (also not from LG), but don't bother with 1.02 as that is the same as LG's 1.02 firmware and probably identical to what you already tried.
Try booting into safe mode first before flashing (i.e. flash in safe mode). There have been a few cases of people who had some driver or other that messed up the flashing process in a subtle way. Their symptoms were like yours - awful burns no matter what discs were used. For these people, flashing in safe mode bypassed the drivers and it returned their drives to proper working condition. I don't know if it will work but I think it is worth a try.
If that doesn't work, try the drive on another system, just to make sure some background driver isn't buggering up things during burning.
And if you still can't get decent burns out of that thing, bin the thing and get a Pioneer (110/A10/111/A11) or a BenQ DW (1640/1650/1655).