Your amendments should always gain support form your specification. Otherwise you are introducing "new matter," which is not permitted. That being said, keep in mind that you can argue support from things like your Figures, etc. If you "showed" something, you may have adequate support to avoid new matter rejections.
You can read the relevant sections in the MPEP, try 7.31.01, where the relevant statute that is cited against new matter:
"The following is a quotation of 35 U.S.C. 112(a):
(a) IN GENERAL.—The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention.
The following is a quotation of the first paragraph of pre-AIA 35 U.S.C. 112:
The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same and shall set forth the best mode contemplated by the inventor of carrying out his invention."