don't have a Z but from the picture, it all looks wrong.
You can expect some carbon deposit inside the pipe which you can just about see if you run your finger inside.
I would 1st check to make sure you haven't overfilled the engine with oil.
Next would be to check for oil leaks just in case it gets sprayed onto you exhaust
Popping on over runs is normal & normally caused by the PAIR system.
I assume you run the standard bike with no mods