Tricky one this! But mine is mounted between the bulkhead and rear of cylinder head.
The CFSV or purge valve is part of the fuel evaporation control system. The valve is opened to purge the fuel vapours contained in a charcoal canister
In order to cut down fuel vapour emissions, a charcoal canister is connected to the top of the fuel tank which allows fuel vapour to be partially absorbed . When the engine is running and at normal operating temperature (but not at idle), the CFSV is opened by the ECU. Fuel vapour is drawn from the charcoal canister into the inlet plenum and is therefore “burnt off” by the normal engine cycle.