Ram 3500 6.7L whistle noise

Looking at buying a 2008 Ram 3500 Dually with a 6.7L. Upon acceleration and on applying engine brake, I can hear a whistling noise from under the hood, like an air leak.
This truck has been modified, DPF deleted and has a Edge tuner installed.
Does anyone know what would be causing the noise.
Any help would be appreciated.
Marcellin

Sounds like turbo whistle.
If it has an aftermarket air cleaner assembly, it's likely you hear the turbo whistling....mine whistles near all the time. The more I mash the accelerator pedal, the louder and more shrill the whistling gets then it changes tone and gets even more louder going uphill wide open.
Does this sound familiar to you?

The air filter is stock. Actually, the first few miles it went just fine, but all of a sudden it started making a hissing noise upon acceleration or on engine brake.
Anyway I am not to concerned anymore. I called the guy back and it was sold. I guess I didn't make up my mind fast enough.
Thanks anyway.
I do have a 2008 Sterling Bullet cube truck with a 6.7L having 80,000 miles on it. Got it new and never put a penny on it. Great truck. That's why I'm looking in changing my dual wheel pickup. It's a Ford F350 1999 with a 7.3L. Injector problems, clutch problems, name it.