i18n search/replace with input methods latin-4-postfix and rfc1345

[B.T. Raven]

I have files with
;; -*- coding: utf-8 -*-
on first line and with many unicode characters. I use either
latin-4-postfix or a lisp routine to input the Latin Extended-A
characters. During an editing session I can search (and replace) only
those extended characters that I have input during that session.
Characters input in former sessions (before a file save and close
buffer) are not seen by any of the flavors of the search command. An
inspection of the characters with C-x = shows that what look like the
same characters have, in fact, different code points.
rfc1345 is not listed among my input methods but I suspect that I am
going to need something other than latin-4-postfix to search for these
characters. I have tried different combinations of unify-on-decode (and
encode) but that hasn't shed any light on my problem. The files seem to
be normal utf-8 files that can be imported into other applications
(Win98) and I can operate on them in emacs (NT build) in every other way
I am familiar with so far, it's just that no searching is possible. Any
suggestions?

Thanks,

Ed.