I am planning on adding a tial on my GReddy manifold and was wondering if I should use a schedule 10 90 degree elbow, use a regular exhaust pipe or weld the flange right on the manifold...or does it even matter?

Will post pictures when it's done.

 

Yea, but typically it requires a little more fab to get it so sit nicely and you usually cant put it near the collector which would be most desirable. So try the elbow if you can fit it.