I had wastegate rattle too. The most annoying sound from a gorgeous car. I spent an hour with a cold nine and the rattle is gone.
I was lucky I. That the rattle was coming from the rear turbo (the one you can see from the engine bay) I adjusted the actuator arm 5 turns and replaced the missing e-clip and voila, happy days!
I have to say, before you go spending lots of money fixing this problem, do a little investigation of your own. All you'll need is a small handled 10mm wrench and a small handled 4 mm wrench for the adjustment. There is so much information on these boards about it.
It may seem daunting, but it's much easier then it sounds and looks.