So ive decided to keep my car (for anyy of those who read the thread) and im trying to create a presise action plan, so im not rebuying parts and what not.

on to my question. my car HAS to pass ontartio etest, which is sniffer test only, no visual inspection. as far as i know anyway, ill definatly find out for sure. i plan on staying N/A for cost reasons mainly. So im wondering what exactly directly effects the cars emmisions output? i.e. compression,boost,heads,exhaust (aside from the obvious,cats, but like pipe sizing, long vs short tube), difference between carb and efi, cubic inch, cam, tune etc...

also with any thing that effects the emissions output, is it a minor change or like a garenteed fail