High EGT, No Boost and a major boost leak!! PLEASE HELP.

[Hammerhead]

I have seen something similar to this about 10-12 years ago...
It was also one of those unbelievably wonderful DuraLite ... ahem "Best on the Market" CAC's.
DuraLite doesn't, or at least didn't used to, weld in the cooling tubes. They use a rubber grommet to seal the cooling tubes into the header manifolds. What occasionally can happen is that the grommet gets nicked, the manifold doesn't get cut right, or after time gets weak, and then holds seal until pressure forces it out of place breaking the seal. Breaking the seal takes more pressure than holding it open, which makes it difficult to find without pressure testing the CAC.
DuraLite's used to be made in Calgary, AB and I've been to that facially before they moved the manufacturing to Mexico. The idea of using a grommet is good as it allows the tubes to flex in the manifold without cracking like OEM welded, but the problem is in order to have enough grommet material to hold seal under pressure they have to space the cooling tubes further apart. This means less tubes, which equates to less flow capabilities. Trucks with large CAC's don't show the effects as much trucks with smaller ones. The smaller the CAC, the larger the percentage of drop by the reduced amount of tubes.
We've asked DuraLite to make one for the T800/C500 wide hood. These trucks have massive CAC's. They are designed for heavy loads at slow speed so the CAC in them is probably the same size or bigger than the rad in a VNL, and because our sister company uses the C500 as Prime Movers they flex the crap out of them so they wanted to give this option a try. They won't make it because it can't meet the air volume low speed heat exchange demands required. What does that tell you?