They are screwed in. There is a hexagonal form to them (on my 2008 model) which you might be able to get a socket on; I think they are approximately 21mm, maybe bigger or smaller than that. The hexagonal form is metal, but covered with a thin layer of rubber at each end. If you can, try to grab them as close to the engine casing as possible. No glue should be involved!
Mine came out fairly easily. I wish I could say the same about the TT rubber adaptors, but I'm trying to remove them at present because a heavy bash sheared 3 of them off, and so far I've managed to remove only 2, using a hammer and chisel (and a Dremel, and a lot of swearing).