Sounds like there is a boost leak. I built my own boost leak tester using some ABS plumbing parts. I installed a valve stem into my ABS plug. You put the plug into the boot coming off of the turbo and then energize it with regulated air...then start listening for air leaks. You can spray some soapy water on the places you think that it may be leaking. Tighten or replace clamps, bolts and gaskets till you have no leaks.