Whatt's the difference in the OBX 4-1 Header and the OBX 4-2-1 Header.

And noticeable gains?

Pros/Cons?

Simply curious because I plan on buying my header at the end of the week. (If not today.) And I've been doin' a small bit of research and came up empty, so I figured I would ask some guys around here.

The only thing about the 4-2-1 Header is that it's a better fit from the O2 sensor to fit into the opening, but that's about it.

All help is greatly appericated before I drop 200 bucks.