I couldnt find any info from searching about adjusting it on light on drives.
Iv got 2 xbox's with light on drivers that are flashed. Both read most back up but the odd back up had glitchs like sound would stop for a few seconds. But there was 1 game opening title gave dirty disk error on 1 and gave dirty disk on first mission on my other box. This lead me to belive maybe its the drive not the disk. I tested on my friends xbox which is a really 2006 model (mine are from 2008) and it worked on his fine.
So started doing search and found out about pot adjustment. There were instructions for other types of drive but not the light on. Well to the point now.
--------- Import stuff below.
You need to turn the pot anti clock wise to lower the ohms, instructions for all the other drives say clockwise. First xbox of mine that was worst at reading was 5.11 and slightly better one was 5.06. (CD pot was 0.76 on both) factory.
DVD pot on the left CD on the right.
I turned it down slightly to 4.86 and 4.91 and they both read a little bit better getting further before dirty disk error.
Then I tryed some more 4.56 and 4.61 and they both almost read perfectly havnt play all the way through the game to see if I get a dirty disk error but they played for 20mins of testing. Just the odd sound glitch like the wind stops for half a second.
I tryed to go slightly lower to get them both to 4.50 but they only seem to change in steeps and the next steep was 4.36 and 4.41 which was more then im willing to push them considering they are only 6 and 4 months old.
Using Verbatim DL 2.4X backups.
So im thinking maybe they have started seting the laser as weak as they can to make it harder to use backups and force you to wreak your originals.