turn the gain don on the boost controler.
il tell you whats hapening. part throttle theres more boost in the piping compard to the manifold...
ie: your got compressor surge. wich is your turbo trying to push more air than the engines using.
please stop calling tis problen r and r, i cringe at the very thuoght of it, that is the gayest term ive ever heard. sory but it shits me all teser wanker terms floating aroud and to every mechanic is painful to read.