03 6.0L no boost

[Lethlic]

Hey all, got a issue with the exhaust i think. Turbo will not build pressure and sounds like its got a leak. But i can't find it. And when i let off the accelerator the turbo "chug chug chug's" its way back down to idle! I'm thinking its actually an exhaust leak from the up pipe, cause i've check all the boots and piping along with the intercooler and can't find anything!

p.s. the truck is stock with a 4" cat back, with the cat deleted, along with the egr deleted.
Any help would be great!