In Reply to Biggest bang is suppose to be from the MESA headers REJohn (SpeedD) [nm] posted by Ole (OLE) on February 29, 2000 at 16:57:06
First off they provided 17 HP on the 5.9 at the rear wheels (dyno and track proven) which is more than JBA or any other manufacture that I know of will give you (in the rear world).
Second they have the best warenty I know of. If the headers fail for any reason, they will replace them for free.
Third is cost per HP. The Mesa Headers are a little expensive at $755 but these are nickle plated, .090" wall tube steal, 1/2" flang and includes the y-pipe or crossover pipe for R/T type applications (dual inlet cat). But this is only $44.41 per HP (755/17). The JBA's on the other hand seem to be averageing about a 9 HP increase w/ y-pipe (I've herd as low as 4 and as high as 12). They can cost about $710 (Stainless Steel headers = $400, $160 for y-pipe, $150 for plating) which is is about $78.89 per HP (710/9). Also the standard JBA headers are not platted, use .070" wall tubing, has a 3/8" flang and they charge you extra for the y-pipe.
So, logically speaking thouse the Mesa Headers are more expensive up front they are cheeper in the long run as I don't know of a mod that you can put on the D that will give you 8 HP for the $50 or so price difference.
As you might guess, I AM VERY PLEASED with my set of Mesa Headers!!
John.