WXR XML Importing Filters tags I need to keep

When I import my WXR XML file it appears that wp_insert_post (or another function) is applying filters to strip "<?php" tags that I need to keep in my content.

I have searched the various wp-include php files to locate:
wp_insert_post
sanitize_post
wp_strip_all_tags

but have no clue as to what files to edit -- and what edits to make to keep from stripping the php tags.

Advice and assistance greatly appreciated. Thanks in advance.