This is the Front Pipe that you need to increase exhaust flow from 4" to 5"

Chev/GMC Duramax 2500/3500 2006-2007
$170.23 $137.80

Get even more exhaust flow with this 4" down pipe with flange.

Chev/GMC Duramax 2500/3500 2001-2005
$152.06 $123.10

Get even more exhaust flow with this 4" down pipe with flange.

Chev/GMC Duramax 2500/3500 2001-2005
$181.71 $147.10

Get even more exhaust flow with this 4" down pipe with flange.

Chev/GMC Duramax 2500/3500 2006-2007
$134.16 $108.61