I had my bike MOT'd today and the mechanic said my CO2 levels were high on the emissions test. They were 7.8 when he would expect 3.5ish. He said this was down to my bike running rich. My spark plugs are a little sooty but i wasnt bothered about it. I suspect a past owner has had an aftermarket exhaust on the bike &must have rejetted to suit. Then when the bike was put back to standard the carbs were'nt. Do you guys think fitting a high flo air filter will sort this out or should i rejet my carbs? Am i right in thinking it would just be the main jets that were changed?