Had to hand the bike over to the mechanic for a few things. After finishing he said the bike is running really lean, saying the spark plugs were white. I have not made any performance mods to the bike since I bought it. The previous owner put on a yoshi slip on, some pod air filters and rejetted. The spark plugs that were in when I bought it looked perfect, a nice golden brown. However I decided to replace them with iridium plugs just to see if they would make any kind of difference (they didn't). So my question is do I actually need to rejet or is it something with the iridium plugs?

I doubt it's the plugs cos i have a Yoshi with iridium plugs(genuine standard air filter though) and my plugs are light brown,indicating mixture is ok.