Before you run out to have the valve guides replaced, consider what Steve Brotherton had to say in this post.
Average price for a valve job
An independent Mb tech in my community who spent the better part of 20 yrs. in an MB dealership told me that he's seen many 103 motors go well past 200K before needing guides.
I had a consumption problem that was cured by new valve stem seals. The motor had close to 100K on it.
1991 300-SEL - Model 126
M103 - SOHC
James Madison - Oppressors can tyrannize only when they achieve a standing army, an enslaved press, and a disarmed populace.
Liberty Firearms Training - After years of trying to regulate California criminals with a never ending stream of gun control laws they have still not given up with the belief that if they make something a crime that criminals will miraculously start obeying the law.