ISX 15 Knocks under load

I have a 2013 pete Cummins isx15 just had an inframe done . New def and SCR replaced .Truck idles good , runs ok in the morning when-cooler outside but once I get a loaded and temp outside warms up truck has a terrible loud sound in the cab . Almost like an exhaust leak , the air going into the air filters seems to be very choppy. I’ll get up to speed and shift to neutral and bring rpms up to 15-16 hundred and noise seems to go away (some what ) Put back into gear and starts again . It’s really bad underload . Shop has run many test on fuel and air but they are stumped to as why it’s making this sound . My truck had been in the shop,since May 10 for inframe and new head. New clutch etc.. most of June and know three days in July cause of this problem . Any suggestions would be appreciated. Thanks

 

The whole airintake system was pressure tested?