Gas Tank Pressure

I installed a new gas tank (32gal) which uses one of the two OEM vents. It seems the generate significant overpressure (positive). Sometimes can hear the tank "pop" as it expands and when opening the cap it vents out air alot. Also, after driving, if you walk within 20' of the vehicle it smells of gas fumes, it will almost knock you down if I park in a garage.

Are the OEM vents positive or negative pressure relief (allow vent air in or out)?

Is this positive pressure normal? The OEM tank will not "pop" due to shape if it had this pressure, but my new tank has flat sides so it does "pop".

Is there some other issue (charcoal canister)?

Thanks.......

How old is your fuel filter?
I actually had one that restricted the flow so much that the fuel pump was pushing fumes/vapor out of the filler neck.