Impex Problem (merging two databases)

[Narutoboy]

I'm trying to use Impex to merge two databases into a blank forum. Every time I try and do it, though, the system will automatically merge certain accounts, while others are completely untouched and given import id tags. For instance, my user id was 4 and my account was merged with an unrelated user on board #2. His id was also 4. How do I stop this from happening?