You can heat up the area around the tube with a torch. If it is an aluminum intake it will be easier because aluminum expands more than steel, so it will get loose in there pretty fast. I would try it with a propane torch; put a vise grip on the tube, heat the manifold at the base, and pull 'er out. I have used an oxy-acetylene torch for this in the past, but the propane torch would probably work too.