Anyone know of a manufacturer that makes headders for the 4.6si? Any experience with gear changes?

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2008 BMW 335I Blue Convert - still in break-in!
2003 BMW Silver M5 W/ 4.11 gears, Cust Exhaust, Software.
2002 BMW Silver X5 4.6i W/ G-Power Custom headers and SS exhaust, Dinan Throtte Body, S3 Software, Super Charger, 4.11 KMS Posi gears, Custom intercooler, Turbo controller.
2000 Yamaha White Road Star Anniversary Full Dress #322
1999 BMW 528i
1990 Mercedes 300E
1989 BMW 325i
1978 Kawasaki 650 Street Racer