FWIW I knew a good head porter here at work, he got after a pair of the latest cast (non 48 degree) W2's 2009ish He was able to get them up to 340 with a 2.08 valve/45* seat. I didn't believe him until i saw them and then we flipped them on the bench. They have a good amount of cross-section from the castings being 'rubbed'/evolved thru the years. Well below that point the typical intake manifolds available would probably be the cork in the system but based on what i saw in the heads I'm sure they'd have enough to make 800.