How can i fix my 1989 Mercury Topaz?

My car sounds like it is running wide open. At other times it spits and sputters like it isn't getting enough gas. I have to pump the gas several times before my car will start and sometimes i have to rev it up to keep it running. But after a few seconds of revving it will usually straighten out. I already replaced all air and fuel filters and did a complete tune-up. Someone said my choke could be stuck but i have not had any experience with that. I can hear the fuel pump when i turn on the key, so i know that it is still working. Could you please advise me on what else could be wrong?