If it's true that MSDS headers flow better, it could be that they have higher quality welds. I've read reports that the WR has crappy welds, leaving flash on the inside of the tubing.

SS is actually a poorer heat conducter than mild steel, btw.

Function before fashion. '96 Contour SE "Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998