How do I backup ONLY the files that change?

[Guest Ceed19]

My SPB backup files were 250 meg compressed. I have gotten it down to 190 erasing useless programs and pictures and videos from my device. But it seems that there should be a lot of non changing rom files that do not need to be backed up.

The way I want to use my backup is the restore back to current state after a hard reset. Is there a way to tell which files are unchanging rom files? If I can exclude the files that are restored during a hard reset and that are never changed by any type of customization or settings then the backup should see a significant decrease in size.

ANy help would be appreciated,

thanks