They do back purge, at least since I've had their stuff. I've had 2 FR manifolds now. They started out with Honda stuff, so you might have worked on a pretty old piece.

Dan covered what I was thinking. 1 and 4 come in pretty steep. What people usually do is join 1-4 together like you did 2-3, then angle those pairs in together giving you a nice square 4-pack. Having said that, just run it. That'll give you a little better tool clearance under the turbo flange, if you weren't going to tap those holes. Speaking of which watch your tool/fastener clearance around the head. Turbo position is nice. You're also commited to running power steering and no AC with this manifold as #1 primary cuts through that space. Welds look great.

If guy on the street has $500 in just materials, why is it a giant mystery why manufactured tubular manifolds cost $1000+. Labor, supplies, QA, and research don't grow on trees!