I am not suggesting your problem is due to plugged air injection passages.

I was actually responding to the originator of this thread.

I would be suspicious, though, of the diagnosis that your left side chain is stretched. Either the chain is stretched, or not. There is no difference between the left-side and right-side. It is one chain. Further, M119 engines don't have the same problem with stretched chains like M116 / M117 engines.

If the air injection passages are plugged, then the head must be removed.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".