Air leak detection - Old school method - Spray(carefully) Quick Start or any starting aid for Trucks around the area in question , whilst(neat English word) running the engine. A sudden increase in engine RPM indicates an air leak. Becareful, one does not want to set the engine bay on fire - now how do I know that.......
Side Note:
For a starting aid on gasoline engines try WD40 in the intake. So this may work as well for air leak detection.
