we've got two issues to solve about customer search:
1) limit the lookup search not to 2 characters as the deafult is (we've got a customer master data of over 700k entries and we want that the db query is run only after at least 4-5 characters, to limits results)
2) show more information in the ajax lookup after the query is ran (we need to show also custom columns that we add to CUSTOMER_USER table)
A third issue is the column over the search query is run, but we found this topic that should help: http://lists.otrs.org/pipermail/otrs/20 ... 03645.html
Hope someone has hints about the first two problems

Thanks,
Luca