I/M update
in a nutshell this is what rich@xcessive had to say...
he's using my oem manifold and photos from mr.sentra specv's manifold as a basis to do a mold then casting of the runners. but, instead of the oem style 2 part runner sections (upper/lower), or multiple welded sections as in mr sentra specv' manifold, he's doing a 1 piece cast runner section, to go with the plenum he already offers. he's got the taper figured out from the 50 (something) mm horns to the head flange. the runners will have some curve to them (like the oem does) so as to clear the firewall better and add a touch of length as well.
then at closing when he said mine will be "the 1st" this tends to make me think he has plans to offer these to everyone, should demand warrant it.
this is sounding like good stuff, guys...stay tuned (pun intended).