Might be when variable intake runner length valve cycles???????

M104 has a valve in the intake manifold that effects a change in the length of the intake air path. Kinda like headers except for the intake side. It's purpose is to tune the intake to match load and RPM. Maybe someone more knowledgeable can explain better................

J. M. van Swaay

__________________
1994 E320 Wagon, 230,000 miles
1995 E320 Sedan, 106,000 miles
1994 E500 Sedan, 79,000 miles