Dx'd with pna 1 week ago and given z-pak, which was finished yesterday. still gurgling cough and metallic taste in mouth. still infected?

Depends: Depends on if you have other symptoms of infection for example Fever/chills elevated white count. If cough is productive you should get sputum cultures done. Repeat CXR to document resolution of pneumonia, also not every cough is pneumonia and viral infections are tend to be more common in this season and not treatable with Abx. Recommend flu test and discuss with your primary.

ToCoughOrNotToCough: That antibiotic will stay in your system for a few more days, which explains that metallic taste. Coughing up a lot of sputum can do that too. And even if the antibiotic killed all the bacteria, your lungs are going to spend the next several days cleaning up the mess and sending it all out through your throat. So don't expect miracles. Also, if you start feeling worse, get back to your doctor.