I have checked it all, its exactly 13 threads, the push rod moves with a distinct stop, either end of its movement range, and I've drowned the wastegate spindle in penetrating spray. I did think there was a possibility of the wastegate being slightly stuck open, robbing the engine of boost but it seems to move freely. Also bear in mind it's a fully reconned turbo from a reputable company with a 2 year warranty, so it should be fine anyway.
I should say, my 'problem' isn't really that bad, it just feels down on power from how it used to be. I'm going to get a new intercooler this week and see how it is. It needs one anyway - as you can see from my earlier post...