First, I've never heard of a CBZ so I'd have to do some research but I assume it's four stroke?
Second, has anything been done to the bike recently? Servicing, modification, crashed?
1. Do you mean the idle is higher than you're used to?
2. I don't understand. You will get sound from the exhaust whenever the engine is running. Do you mean the sound is different than it was or is there another sound that isn't the exhaust note?
3. I can't help with vibration (it's not something I notice unless it's extreme) but maybe go over the bike and make sure all the fasteners are tight and nothing has fallen off.
4. Is the maintenance up to date? Fresh oil and filter, new air filter, fuel filter, spark plugs, valve clearances etc? If you raise the wheels and spin them do they spin freely?
You would need to tell us where any noises are coming from, and then we might be able to tell you what things to look for.