Does a return type fuel system need to be vented?

[RedGTS]

As I understand it, the stock Viper fuel system, like most all newer cars, is not vented (and in fact most cars now will set a check engine light if you don't get the gas cap secured correctly and the system detects air getting out). But most or all of these cars also use a returnless fuel system with no fuel being returned to the tank. If you convert to a return style system and are circulating extra fuel back to the tank, could this potentially cause too much pressure to build up so that it would be a good idea to use a vent, such as a cap on the existing fuel feed line that will allow some pressure to escape?

[Joel]

The standard set up is vented to the charcoal canister at the front. You will need a vent of some sort, but preferably with a roll over valve.