Large amount of Carbon buildup

Is your 2015 CX-5 running fine? What's mileage? Maintenance history? You may or may not know that positive crankcase ventilation channels combustion blowby gasses getting past piston rings as part of normal engine running, are fed back to the intake manifold for recombustion as part of emissions control. Exhaust gas recirculation feeds exhaust gasses to the intake manifold to lower combustion temperatures. These two sub systems creates carbon deposits in every intake manifold, coating the walls and back portion of the throttle body. As long as the engine runs fine, returns acceptable fuel mileage with zero issues in all driving modes from cold engine startup to hot humid days of driving with or without ac, the engine doesn't know its intake manifold is coated with a greasy, oily, black mess. While it may be an eyesore, if the engine runs fine, either leave it as is or spend diy time and money removing throttle body and intake manifold for cleaning. Solvents and/or sand blasting. Please remember, once cleaned, the engine will continue to coat the intake manifold.