skunk2 first gen manifold and skunk2 pro series is the same. There is a thread on honda-tech about this, the only differences on the dyno was 0.0000009 or something along those lines, you just get a pretty skunk2 pro blah blah on the mani.

And yes, skunk2 is a replica of the ITR. If you have a b16 head, then go with the ITR, but if you have a gsr head, then go with skunk2. If it was me, and its a gsr head, I would go with AEBS because the runners are matched to the head which maximizes combustion unlike blox/skunk2.

Also on a side note, putting this manifold on would decrease your low end but you will gain a noticable differences in mid range to top end. For a B16, you should just stick with the stock B16 manifold IMHO.