Honda16hb

I'm in an emissions class this semester so I can offer some technical insight. Running rich will get you high HC and CO output (typically high HC all the way through and high CO in upper rpm range) running lean will get you lots of NOx because that is produced at high temps. Without a cat you are completely fucked. The ideal air to fuel ratio of 14.7:1 is entirely due to the efficiency ranges of the cat.

If anyone has passed smog without a cat let me know, I'd like to hear your story.