Show dialog gauge while preserving function exit code

This function sends api requests.

api_req() {
    # req 1 else return 1
    echo 33
    # req 2 else return 1
    echo 66
    # req 3 else return 1
    echo 100
}

This will return 1 when any of the request fails. Now, I want to pass it to **dialog** gauge. Like this,

if ! api_req | dialog --gauge "Sending requests" -1 -1 0; then
    echo "api requests failed!!"
fi

But it can't detect the fail. I also tried api_req > >(dialog ...), but this way the dialog is not shown. How can I get it working?