I removed the fuel rail this morning, it came out quite easily. The most work went into removing the portion of the engine harness that was in the way.

After removing the rail I noticed that injector 5 was missing the bottom O-ring and retaining clip. I found the O-ring stuck in the cavity but the clip is nowhere to be found. I attached a thin pipe to my vacuum cleaner with a stocking as filter and after about 15mins I only extracted little bits of hard crud. I assume this is whats left of the clip as the bottom of the O-ring is burnt hard and the top is still a bit soft. This might be the cause of the funny sound emanating from this cylinder, it sounds like piston slap, yet doesn't sound like piston slap.

Fuel rail:
https://www.dropbox.com/s/1sixds1cn0xbtf2/20140202_150132.jpg

Injector 5:
https://www.dropbox.com/s/c6q9wbvw98cjxvn/20140202_150244.jpg

Im going to have to remove the head on bank 2 to see whats going on in there, something I was avoiding. Im also building an injector cleaner to properly clean the injectors and test them afterward.

This simple job just turned very big....