You have been here long enough to know about re-mapping a Zed. Please tell me you at least did some research on re-maps before you decided to let someone near your car.
I can only hope the garage you are talking about are using Uprev. Otherwise.....well, I wouldnt trust them, or anyone for that matter.
if you are remapping the OEM ECU, then pretty much only UpRev is the way forward.
As for power gains (assuming its Uprev you are getting), what supporting mods do you have?