Hi,
glad to find all these experts here.I have a bunch of questions regarding my 300SDL.
Overall an awesome car but here some of the problems:

1.Small oil leak.I was told is from the head gasket.One piece of advise I got is don't touch it unless it's pouring(it is not)
because other issues can come up when the job is done.True ?

2.Learn from this forum about EGR valve problems.How can I tell if mine is OK ?

3.I had a diff put in(used).When I go from reverse to drive I hear a big clunk.Too much play ?

4.Two weeks ago my rpm went suddenly up to 3000 for 20 seconds or so.It did it again last week when climbing a hill.I think the transmission went in the lower gear.Any ideas ?

5.The shifting is kind of abrupt.Last time it was a vacuum leak.I have the feeling that the major problem is finding someone that can properly troubleshoot the shfting issues.
I do have a tiny transmission leak.Mechanic fixed the wrong thing and now i have to take it back for some other seal.Is there a systematic way of troubleshooting the shifting ?

6.Also I noticed on this forum about the noise level (very quiet compare to 5 cylinder)My car has appreciable noise exhaust .I have not driven another 300 SDL so I can tell if its normal.The car does not have a trap oxidizer or catalytic converter.
Do they come with catalytic converter ?
Can this be the cause of the noise?

Thanks very much.Great forum !!
John