Under 'Saved Data Indexes' there is a section for 'Auto', which will create indices for fields used in Record Selection formulas.  If you use stored procs to filter the data, the Bursting index doesn't seem to help, but if you return lots of data and then use the Record Selection Formulas to filter the data, it would appear that Crystal will create an index on its temp tables.  This will speed up the selection process as Crystal won't need to read each and every record, it will be able to select more rapidly the records that it needs.  The rest of the report (formatting) will proceed at the same speed...once the data is retrieved (I'm guessing)

 

This only a guess, as I have never used/seen this option before.