Renntech headers 11hp gain 20lb-ft
$3580 + postage.
PLM, 12whp, 11rwtq
half the price.
I personally wouldn't spend close to 4k for for 11hp and pay for a brand.
if you're patient you can find some every now and then $1k for used. same part number off older e63 6.2l and CLS 6.2l
thunder exhaust from Taiwan is $1600. much better flow. let the others pay for the brand you buy the part when they're done with it.