Post this in the Diesel forum for more experienced discussion.

IIRC some 616s don't have a throttle plate. These engines are fuel throttled. I don't know what the air throttle plate is for. It might be possible to cut down a 617 turbo intake manifold which tucks tightly to the head. Do you have room for a one cylinder longer 617 instead of a 616?

This picture shows the manifold. It doesn't stick out more than the upper hose fitting -



Sixto
98 E320s sedan and wagon