When I pulled out my stock WGA and replaced it with the ATP, I didn't see anything that would lead me to believe it was adjustable. Just how would one be adjustable anyway?
The only thing I could see is the length of the rod being adjustable, but that doesn't really affect boost. There is really only one length that works so that the WGA is mounted properly and the WG is fully closed when there is no pressure on the WGA.
BTW, anyone have a clever way to keep the rod from rattling? It's just held onto the WG lever with a pin so it is free to wiggle a bit and rattle. Perhaps if the rod was a little longer it would press against the lever at rest, although too long and your wastegate would be cracked at zero pressure and your spool would be awful. Maybe this is what they mean by adjustable.