A question for all you "experts"
 

The situation:
One of my turbo blades was damaged causing the bushings to wear out causing a lot of smoke. There was enought oil to cause an oil streak to form at a minor air leak by the IC. I'm currently replacing everything but I noticed when I pulled off the injector assembly the front injector was clean but the rear injector was coating with a black carbon deposit. So is this coating from the oil or is it caused by something else?
So put on your thinking caps and let me know if I need to check something while I'm re-assembling everthing.

Thanks.

Time to check the compression. You may have a bad rotor back there.