air noise at heavy load

[AStewart]

I have a loud air leaking type noise near the pass floorboard under heavy load. It only does it pulling my 5er on a grade. If I back off it goes away. It sounds like the evaporator core but it has to be from the turbo. I have checked the hoses and clamps and it all looks good. I have a Quadzilla xzt towing chip and a modified air box (hole in the bottom with hose going down).

Thanks



2005 50K mi.

2500 4X4

285s AT2 Michalins

33' GearBox 12000lbs. GVW