The M103 engines are very notorious for valve seal problems.
M104 and M117 engines have virtually no problems with wearing out valve seals, except I suppose at extremely high mileage, and his car is just broken in.
If he had worn out valve seals, he'd likely find oil on his spark plugs, and be consuming oil internally.
I don't think valve seals are his problem.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".