I'm struggling to understand why the dpf delete causes more diesel smell. Is the cat part of the dpf?

I had a 1996 ford crew cab diesel dually with the 7.3 turbo diesel. My cat ran away and I regretted not having a better leash every day after that. The smell was terrible.

I understand getting rid of the dpf but not the cat. Help a non-e70 x35d owner understand the relationship between the dpf delete and the smell issues.

Side note: I had a four position switch on the ford; one being daily driving, one being towing, one being for emissions testing (dyno sniffer test) and the last being what I called global warming or block out the sun setting. ;-)

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Kirk
Las Vegas
2016 X5 40e Mineral White/Black Dakota Leather, ZLL, ZCW, ZDA, ZDB, ZPP, multi contour seats, rear side window shades, HK stereo
2011 E90M3, 6-speed manual