Hello, for the noise, what made you decide to replace the drive assembly? Before doing that did you try swapping fusers? And yes you are correct replacing the drive assembly is not for the faint of heart. I think you need to go back to square one swap the original assembly see if there is a change. As for the DC controller and lasers issue I would check connections and swap with the original DC board as well, because if it was not having issues prior and now it is I would assume it was because of all that went into taking that assembly apart. Also, were you careful with the boards? Have to be careful you did not burn one of them out. As for the 99 error, you may need to do a partial, or full disk clear and reload firmware. As for the scanner not getting power I would check the scanner control board connections make sure they are all seatted properly.
Hope this helps.....