it's probably your chain. if it's really shot, it'll make a bunch of noise no matter what you do to it. grab one of the rollers on the chain, if it has a bunch of slop in it, it's probably shot. always replace the chain/sprockets as a set. putting a new chain on old sprockets will eat the chain in a hurry, and vise versa. if you need someone to replace the chain/sprockets, let me know, i can do it for alot less than any shop. if you have the parts in hand, i can get it back to you the same day you drop it off, as long as it's somewhat early when it's dropped off.
you can get a chain sprocket set from any decent shop for about $150-$200, depending on what kind of chain, and what size/material the sprockets are. labor wise (foor me to do it anyway) it'd be in the nieghborhood of $50 or so.