Originally Posted by BigRed
How does the EGR system on my truck work then?
It doesn't have one. Manufacturers use EGR when they need it to control NOx. If a company can meet the emission standards with cats, calibration, etc., then it won't have to pay for the initial expense and warranty coverage to support other components like EGR. Apparently, it was possible to certify the 4.0L to the 2003 standards without EGR.