Diesels do not have a catalytic convertors.
However, Cummins did install an EGR on the 8.3 in 2002, though that doesn't mean yours has one. Best to have someone look at it to confirm.
1998 – 2002: Cummins introduced the ISC Engine with CAPS (Cummins
Accumulator Pump Sysem) fuel injection system. This was a
computer controlled injection pump w individual lines going
to each injector. Upgraded to 24 valve head and
implemented electric fuel lift pump.
2002 - : Cummins Introduced the Cooled EGR emission upgrade to
reduce NOx.
EDIT: I stand corrected. Even at my old age, one has the ability to learn something new and enjoy eating crow smothered in catsup.
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