need answers on radiator caps

hi
just wondered what pressure radiator cap the eb to au should have as the ea 3.9 uses a 110kpa/16psi recovery and ed to au 4.0 uses 120kpa/17 psi and ba to fg uses 120kpa/17psi recovery cap
those specs above is what ford specify
would using a 120kpa/17 psi or a 125kpa/18psi cap be ok in the eb to au
what causes a hiss for a couple minutes after a drive at times with a 110kpa cap on a e series 4.0 will a 125kpa cap fix that or do they damage stuff
how much difference is 18 psi over 16 psi
and how much difference is 20psi over 16psi
just wondered what pressure radiator cap the eb to au should have as the ea 3.9 uses a 110kpa/16psi recovery and ed to au 4.0 uses 120kpa/17 psi and ba to fg uses 120kpa/17psi recovery cap
those specs above is what ford specify
would using a 120kpa/17 psi or a 125kpa/18psi cap be ok in the eb to au
what causes a hiss for a couple minutes after a drive at times with a 110kpa cap on a e series 4.0 will a 125kpa cap fix that or do they damage stuff
how much difference is 18 psi over 16 psi
and how much difference is 20psi over 16psi