How does carbon builds up in a vehicle?

How does carbon builds up in a vehicle?
Carbon will build up in your throttle body regardless of what you do. It is one of the byproducts of burning gasoline. Most manufacturers recommend having a fuel injection cleaning done every 30,000 miles, where you manually clean out the throttle body, run a pressurized detergent through the intake, as well as put a fuel injection additive in the gas take.