If you're talking about the small audible pause that occurs when moving from one performance to another, this is entirely due to the effect algorithms changing. When you change from one perf to another, the audio output is muted for an instant (if this didn't happen you would hear all kinds of unpleasant noise from the DSPs). Most synths behave in a similar way in performance mode for this reason. This is not something which would be improved by adding additional memory.
If I remember correctly, (it's been a while), you should be able to minimize this delay by setting up performances that use the same effect algorithms (you can change the sends and effect edit parameters - just make sure that the actual effects themselves are the same for every perf you're using). This basically allows the effects to "recover" in the quickest possible time. As long as you're not using performances that rely heavily on effects, you should be able to re-program those performances you use most often to use essentially the same effect pairings.
Also, you might try using the USER PANEL feature as a quicker way of selecting performances (faster than the keypad). You can set up user panel presets where each preset allows 16 performances of your choice to be selected directly by pressing the buttons beneath the sliders.
Hope this helps