promotes the mixture of air and fuel

reduces intake noise

cools the intake air to a suitable temperature

distributes intake air equally to the cylinders

one

two

four

eight

regulates the intake air flow rate

reduces the intake air noise

enhances intake efficiency

regulates the intake air temperature

optimization of exhaust efficiency

reduction of exhaust noise

reduction of nitrogen oxide in the exhaust gases

reduction of the exhaust gas volume

recirculating exhaust

using catalytic converter

using some additives in the fuel

none of these