Going to use the maf housing and an airbox from the E53 4.4 model to keep it all tidy.
Reducer off the turbo into a 3 inch pipe then to the maf and box being 3.5inch.

Nice! Are you going to dyno before and after?

Tune and dyno at the end of build. Will fit everything to see how it runs and fits they probably remove parts again to run until remap.
There are loads of things needing done to just having it run better, like electric fan for the belt one, earthing wires, egr removal, hoses, rubber seals on inlet manifold etc. 17 years old now so everything on the car that hasn't been replaced needs to be replaced.