Upper performance in AutoCompleteBox

I have modified the LA-County searches and have noticed that performance is much slower when Upper() is added to the AutoCompleteBox where clause.  I'm attempting an owner name query on a parcel layer containing 225,000 records in a File Geodatabase.  The data in the owner name field in the File Geodatabase is all upper case.   Without the upper and typing in upper case characters "SMI" (as in Smith) the AutoCompeteBox performance is almost instantaneous.   With Upper() and using lowercase characters "smi" the AutoCompleteBox starts returning results after 3 seconds.  There is a noticible difference in performance.  Does anyone have any ideas on how to improve AutoCompleteBox performance when using Upper() in the where clause?  

Thanks!

Dan