This just happened to me a week ago as well and it was a pain to find. Just as Krazyd27 said check ecu (first thing I did) and mine came up with 55 (no error) and just like you the same thing was happening where it wouldnt boost and it would sputer so I went through everything redid some hose clamps fixed 20 vac leaks now it boosts to 14 and runs smooth. ( I have a problem with my ecu the injector map is messed up so it will miss sometimes but if you have a good ecu this will help.)