Engine/Transmission (1994 - 1998) Rattlesnake in my turbo?

[gary johnson]

Well, sounds like it.....I have Industrial Injection Phatshaft with about 3k miles on it and lately have some serious noise and choking as I give it throttle. Happens mainly when I shift into 5th gear and I'm at 45 mph giving it throttle. Literally sounds like a mean *** rattlesnake, then as I get boost up, turbo lights and the noise is gone until I let off the throttle. As I do, rattlesnake is back! Sometimes I get a "coughzzzzz' from the turbo, similar to retarded timing on an old gasser ...it'll cough through the carb.
Thinking a gasket problem, I installed new ones on exhaust manifold, turbo flange and O ring on turbo elbow. Still get that damned rattlesnake!
Any thoughts or cures totally welcomed! ( No problem with boost as turbo lights around 1750 rpms)