the one vnt-15 i had rebuilt at http://www.xsboostturbochargers.com/
for 350ish, this was with new/rebuilt vnt sectiion.. id hear a odd click/clack once in a while...
but i ran tests with a boost and vacume gauge at same time.. boost for boost level and vacume gauge T'eed into the vnt to see why id get limp.. all systems 'functoned" via gauges but boost was too high.. so at that point it was turbo time..
via a forum of local vw people someone posted a link to the place above.. i went in person to check them out.. their webpages suck... very impressed.. they balance/clean it all..
now before you do the its a turbo thing.. do not be like my usless stealership and go its a turbo... how long since the intake was desludged?? if its "restricted" it will do all your faults... if thats done... then see what boost vs vnt vacume is.. if thats right seized vnt ist possible..