Thanks for response.
I used MediaCodeSpeedEdit V184.108.40.206 to patch firmware, so theoretically it should work. Actually drive was flashed with modified firmware for the first time in less than half an hour after delivery
masotime - your theory seems to explain it; lead-in seems to take pretty much time. Before creating test disc with nero, I had max 16x listed in disc info, and after burning, there was 8x in the same place
4x media I tried to burn at 16x, was just to test. It was LEADDATA1, which is so bad, that it's hard to get reasonable results even at 4x. I just wanted to burn TDKs at 16x.
Anyway, could someone tell me that it's certainly not hardware fault?