I have a 95 6.5 c2500 with a NV4500 and it sounds(the turbo sound completely goes away) like the wastegate completely engages and dumps all the boost once i hit a certain amount of boost, but i don't have a boost gauge to verify this...its usually around 2500 rpms, I'm just wondering if its something to do with my wastegate acting up, starving for fuel, or something else. it might be completely normal, can someone shed some light on this for me?

 

This is a common problem with the factory boost control. The pcm sees too much boost or too high intake air temps and cuts the boost, usually when you need it most. 2500 is out of the stock turbo's efficiency range anyways. My advice is get that piece of crap off of there and replace it with a Holset hx40w or something similar. If you decide to keep the stock turbo, you should atleast ditch the factory vacuum controlled wastegate system. You can build your own manual controller or buy one. Your gonna need a boost gauge to set it correctly.