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

between the fuel filler pipe and fuel tank

in the fuel tank

on the distributor mounting in the engine compartment

on the engine compartment bulkhead