Spark Plug for 4AGE BT 20v engine is IK20.
For further information, u may refer this website
http://www.globaldenso.com/en/products/aftermarket/plug/basic_knowledge/heatrange/index.html
It's not about Airtrek but more in general. My Airtrek comes with clear windows (local USF car), but I've tinted the rear doors, rear side panel and rear windscreen 75% tint. Using it for 4 years now, no problems...