Import WordPress WXR – Page IDs Changed

I used the export/import options under Tools to generate, export, and import a WXR file from one WP install (my staging server version) to another (my live site version).

Nearly all of my page and post IDs remained intact. However, a few page IDs were not retained… seemingly randomly, a few pages were given new IDs (the next available ID #s in sequence).

The problem here is I am using page IDs hard-coded in my template files for various purposes, such as navigation etc.

So two questions:
1. Any idea WHY the import would drop the original IDs for just a few pages? What sort of reasons might there be for that?

2. Any way for me to change the page ID for a few specific pages on the imported site? That would be preferably, as opposed to having to edit the templates (and thus having two different versions of the theme which I’d have to then keep track of for future updates).

Thanks for any suggestions and assistance!