PETROMARK® 10251 AIR INTAKE CARB & CHOKE CLEANER dissolves gum, carbon and varnish deposits without dismantling. Not harmful to catalytic converter. Reduces the CO and HC levels. Only for petrol engines! Directions for use: Carburettor petrol engines: Spray inside carburettor and linkages, remove air filter and spray the liquid on the throttle plate and air intake. Injection petrol system engines: Spray the liquid in air intake pipe and open end of the PVC valve.