I agree with pmizell.
Many of the members here suggest from time to time about replacing your timing chain and tensioner, but the techs repeatedly say they never, ever replace timing chains on the M103's and M104's. However, the tensioners do go out and the chain rail and guides do get old. I'd just replace the tensioner and rail guides.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".