If you have a chance to get your Iranvisa in Delhi, get it there. Islamabad is notoriously slow. In 1999 it took 21 days of waiting for my visa. I'm a Canadian citizen, and had to produce a letter of support from the Canadian Embassy in Islamabad. The same waiting period applies here in Canada (Ottawa), and also in Beijing, as I personally found out. Best to get your visa before leaving home (New Zealand??) But beware: Iranian visas a valid for three months only from date of issue, and they cannot be simply renewed if outdated. The whole process has to be restarted from scratch, including the long wait. I think they send the application to Tehran by camel express.