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Others have far more experience with this than I do, but when applying for a mortgage I think it's not uncommon to have them require you to drop all AU accounts, thus forcing your report to be a true reflection of just you. Mortgage lenders aren't dumb and know that AU accounts can artificially inflate a credit profile. It's not just about score. If I were you I'd suggest focusing on other things to increase your score outside of AU accounts.
Where do your FICO scores currently stand and what is holding them back? How does your payment history look and what does your utilization sit at currently? Those 2 factors alone make up 2/3 of your FICO scores and together can impact a score +/- 200 points easily.