It is not meant to be reused. The FSM has a black diamond next to it, indicating it's a "non-reusable part".
I had to pull my throttle body off to change my injectors. It had only been installed for a month and zero miles. I replaced it. I probably would have reused it since it was so new and clean, but it was a fresh rebuild on the engine. I have a "shop spare" now.
My experience is that you can't clean them effectively without removing all the rubber coating, so you use a new one.
EDIT: Oh yeah, could you please add some simple vehicle info to your signature? For all I know, maybe you could reuse a t-body gasket in a different year than mine. What year?