Doomdark, I have learned that during beta-testing of EU, Shia nations [Mameluks and Persia] received 1 colonist per year from religion. It was supposed to be used for religious conversion, but AI failed to use it adequately and Shia nations were left without colonists. Analysing history of Iran "Persia", I have read that after the conquest of former Persian territory by Safavids led by Ismail in 1501, and after he was proclaimed Shah of Iran, he declared Shia Islam the state religion and used proselytizing and force to convert the large majority of Muslims in Iran to the Shia.
I played several games as Persia and now I am even writing and posting an AAR on Persia. I had only one event [I think it wasa random event because I only had it only once and not in other games too] of Conversion of Heretics. During Ismail's rule all Sunni provinces [with Persian CB shields in the game] were converted to Shia sect. I think it should be added to the list of historic events several conversion events, so that by end of Ismail's rule all Persian national provinces would be with Shiite religion.