X2 - siamese behaves differently. Bell says that the siamese intake port area should be slightly larger than the intake valve area. Example: a 235 with 1-7/8" valve is 2.76 in., which is impossible to cut into any 235 head casting.
The behavioral difference will also vary based on the firing order separation between cylinders: in an L6 the #3 & 4 have equal 360-360° intervals, the others have 240-480° split.
Even more difference for an L4 because the interval is much larger.
The typical siamese port does have an advantage: the cross-sectional area between the seats is huge compared to the bowl in an IR port, but the entry shape is poor.
