Hello jon,the linkage moves a ring inside the turbo which in turn moves the vanes, so the linkage actually moves it both ways.Have had two cases where an overboost code was set and the vehicles in question kept going into limp mode.Tried cleaner with no luck,then dismantled turbos and found the inside to be all pock marked causing the vanes to stick.One was a rav4 (replaced turbo)the other was a golf 2.0 tdi,which I cleaned up and reassembled,that was 18 months ago and I'm still driving it around now.Not sure if something went through the engine or if a piece of blade broke off,difficult to tell as all the blades were slightly damaged, but it does'nt seem to have affected performance.