its all about location location location.
SMIC dont get anything like the airflow witha stock set up, you need a louvred wheel arch liner as a start to see any cooling increase.
the FMIC has a bigger surface area, probably a thicker core and gets the flow straight through. even a poxy FMIC will work better than the stock SMIC ....IF it is plumbed in right and doesnt have a massive pressure drop. Huge cores on stock or even mapped stock turbos can create as many problems as they get rid of. pressure drop and delayed spool and throttle response as a start.