Modern vehicles have a non-vented gas cap, instead of venting the fumes directly to the atmosphere, the tank is vented to a charcoal canister to absorb the gas fumes. The canister is then in charge of keeping the tank in a neutral pressure. I think the gas cap on my '57 might be original or at least from that era of vented caps, it has a leather gasket and a simple hole in the center of the bottom. I have no odor from the cap and no issues with pressure or vacuum.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy