I've done some searching to find out HOW the plenum spacer works, and now I need to clarify a couple things.

1) Do the flat ones work just as good as the angled ones? Who manufactures angled ones, and who manufactures the flat ones (same height all around). Do the flat ones still solve the front 2 cylinders from oxygen starvation?

2) Does it matter what material they are made out of? I see some are made out of hard plastic, some aluminum.

3) Why are some brands better then others?

I'm not going to ask about thickness, as there seems to be alot of discussion about that.