"Scored" Cylinder

[/font]Hello all. I have a 2007 E92 with the N54 motor. I have been having the typical injector problems, and have been replacing them as they went bad. I was down to two (#5 & #6 I believe). My mechanic calls to tell me he noticed some metallic sludge in the cylinder upon removing the injector in #5. He tells me he has boroscoped the cylinder, and he is sorry to report that the cylinder wall is "scored", and that the only fix is to replace the motor (~118,000 mi). The car doesn't smoke or use oil. And the car runs smooth as silk at lower RPMs. Yet when I accelerate hard, I get severe missing - just like when the other injectors went bad. Has anyone else heard of this problem? I have had the HPFP replaced. I get codes when this happens, but they all involve the VANOS and the charge air gate....no cylinder misfires are recorded. I am confused, and refuse to take my car into a dealer without some knowledge about what's going on. You'd think if a cylinder was compromised, you get rough operation all the time. And if the cylinder wall was damaged enough to lose compression, it would smoke like a crop duster. I got none of that. Any advice would be greatly appreciated.