Do you need to use the Ho manifold for packaging reasons ? Ie do you need the over the top design ?

The Focus Rs inlet will flow your 400bhp, bolts directly on and can take a variety of injectors. And I would have thought 630cc would have been ample ? They tune the mk1 Rs to the 300’s on the Oem 440’s

The Rs manifold isn’t anything fancy but it does have couple of extra bracing brackets.