Definitely not in the cat, as the excess fuel gets burned there. And I'm suspecting that maybe his problem is in one cylinder (if not overall) so that there is excess oxygen and thus combustion continuing in the exhaust ahead of his cat. Even a bad, or using no exhaust manifold gasket, or bad torquing/cracking the manifold, could be contributing.
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Original owner
1990 Nissan Hardbody, Aztec Red
Standard cab, 4x4, KA24E, 5-speed
Intentionally near-stock 
Mods: Second OEM horn, stereo/speakers/sub,
mud and snow tires, HD trailer hitch (cat 3+),
liquid bed liner, G1W dashcam
Definitely not for sale!  |