hey mel,
at my center (which would likely be your center, i'm guessing) they recommend your weight be at least 18.5 BMI. however, they don't push the g-tube necessarily -- instead, they have you meet with their nutritionist who tries to work out a plan with you. basically in my experience, all decisions like g-tube, ports, when to do IVs, etc, remain between you and your CF team pre-tx. the tx center is very minimally involved in dictating your care before the surgery, though you are followed by a tx pulmo and they sometimes do things like prescribe pulmonary rehab or other programs to get you healthier. i'd imagine if you were severely underweight they would require you to do something about it before they would consider listing you, but i'm very skinny and below the recommended threshold, but it's still left up to my CF doc and me how to deal with that. my tx doc has yet to prescribe any drug or treatment other than the testing necessary for listing.
as for ports and g-tubes, i have no idea on the latter, but i know my center removes ports during tx surgery or right after if possible. as patti said, it's b/c of infection risk. i just lost my port due to infection, but basically i've been told it would be pointless to get another when i'm waiting for tx anyway.
hope that helps. if you have any questions specific to the NYC center, please just let me know!