shorties are the way to go After doing tons of reading it all boils down to these three websites and a loss of 10 hp which wont matter if you are leaving the stock restrictive cats on anyway. The extra horsepower is coming primarily from the exhaust leaving the engine faster through the larger tubes, and an ecu tune. Also here are some 55 pictures of there Renntech headers, they look very similar.

http://www.dinancars.com/whitepapersFile.asp?ID=3

http://www.mbworld.org/forums/showth...=222313&page=2

http://www.mbworld.org/forums/showthread.php?t=206642