First, open up the Katapult configuration dialog (try this if you can’t find it) Now you have two options.
The first option is to just disable the Amarok Catalog entirely, by clicking on Catalogs and then removing Amarok Catalog from the list.
Or, you could click on Amarok in the list, and then change the number of characters before searching, which should dramatically improve your Katapult speed.
Personally, I just disabled it, because I have little interest in searching my music collection through Katapult… but that’s really up to you.