Not knowing much about trucks, especially not much about heavy modern trucks, I have done some research.
Semi-sized turbo diesels generate a lot of power, and can be identified by air cleaners on some models. The image below from this site shows two intakes coming from the cab for the air filters. I plan to put external air cleaners on the trukks I am building (progress thread here.)
Example external air cleaners in this thread, which has some of the following pictures.