In the past couple of years the quality of our fuel has changed drastically in different regions of the US. It changes from summer to winter and seems to be different in Los Angles or Maine compared to Texas to Alaska. To keep up with the Government mandated leaner, oxygenated fuel we have made 3 increases in jet size to accommodate the new fuel. A properly jetted carb, that worked great a couple of years ago, may have lost some of its performance due to the new fuels. There are several symptoms, needing high idle, hesitation on acceleration, a flat spot around 2500 rpm, or surge a a certain RPM. Any modifications used to increase performance such as headers, electronic ignition, free flow exhaust, snorkel will definitely affect carb performance. It comes without saying that a bigger cam, reworked motor, or a bored motor makes a difference. We all know that altitude and extreme temperature or humidity affects the air to fuel ratio. Now, if any of these factors are combined, there is an extreme affect when combined with lean fuel. Weber recognized this and has designed a kit to have a variety of jets for all circuits available when tuning your engine. Our jet kits come with simple tuning instructions and a variety of jets to cover the stock and modified engine. We have designed these jet kits from years of experience jetting carbs on engine all over the country with all types of modifications. If you are experiencing any of these symptoms from your weber carb or simply want to improve the quality and performance from your engine, then you NEED this kit. Pick your carb below for the appropriate Jet Pac.