Ohh, evil puddles of gas all over!
I can't imagine that manifold being as good as a pair of SU's! Off the top of me head:
1: it's drawing thru both chokes at once, so it'll be too much carb, per cylinder...
2: #2 and #3 get a better shot at the carb, and will probably run richer, while 1 and 4 have to flow thru the plenum, and get more air and less fuel.
3: airflow changes direction in the manifold, allowing gas to drop out of solution.
4: The FI manifold is a dry manifold, never designed to have fuel in it at all, so all bets are off, there...
5: it's huge!
6: I don't have it to test it!
Toby
66 fi'd sedan..