Question: I am about to enter Iran with a vehicle that needs unleaded fuel because it has a catalytic converter. It would make for a very expensive trip if I had to replace the cat afterward. I've seen plenty of new cars in Iran that would suggest have a catalytic converter. If there is only the "old style" leaded fuel available (which I assume the Paykans use) their cats would go bust. So do you have any ultimate answer? What should I really ask for at the gas station?

Answer: According to the national Iranian oil products Distribution Company there are two types of Normal and Super petrol and both are unleaded.Unleaded petrol/gasoline is called ‘Benzin-e Super' and it is now very expensive for most average Iranians and is not available everywhere. "Benzin-e Super" is just high grade 95/98 octane ''leaded fuel and not unleaded fuel.
It is better to get the catalytic converter removed. Iran has no exhaust fume testing - most likely lots of catalytic converter are already ruined without any consequence.