so i put a technigas next exhaust on my 2007 sprint. It seems the collective opion is that i should upjet. I checked the sparkplug and it seems to be a healthy brown color but im going to upjet 2 sizes anyhow. Is this a actual metal jet you have to buy? i thought it was just a nozzle i could turn a bit to allow more gas into the carb...anyhow i know the stock size is a 55(whatever that means) and i plan to go to a 57.