That's not my decision to make if you know what I mean. You can try to rebuild it, replace with the same or purchase a new one from another manufacturer. Going with the last one will involve possibly a lot of work in fabbing up a new mount, a new throttle linkage, possibly a new flex cable but where the real fun may be is in putting in a new exhaust system.
Now, if you really want it to haul butt, Nova Rossi has a wicked .28 but may be a bit more than the hull can handle especially if you're having handling problems now. What the price tag is I don't know but you can contact Glenn Quarles from his site, www.novarossi.us . You won't find it on his site, he really needs to get it up to date.

There are a few members here have dropped an OS .46 in their TC-31's just as a side note.