The EFX you are using in the performance mode is the same of the patch mode?
The XP 30 have 1 EFX for all parts in performance mode, so when you select a patch, it sounds different due to overall EFX setting. You can define if the source of EFx is the patch or the performance; in case of patch EFX, the source can be any of the 16 parts.

C079 Jet Str Ens use Tremolo Chorus EFX, when you assign the patch to a performance part, it may be using a default EFX for performance mode (example: Stereo EQ).

Mgomes