Well the wastegate is integrated onto the turbo and cannot be purchased new.
If you rev the engine up and watch the wastegate rod it should move.
You can also remove the turbo inlet pipe and feel the turbo shaft for excess play.
Is the vehicle smoking?
Have one person revving the engine a bit on and off while you observe the wastegate rod, it should move when the RPM is increased and decreased.
Check the shaft play on the turbo.
Remove the hose that runs from the turbo to the air filter housing.
stick your hand down in the turbo inlet and jiggle around the shaft. There should be no to VERY minimal play.
Well you can check vacuum at the wastegate diaphram. Im not sure the specification on how much vacuum should be there, but as long as its getting a vacuum it should be fine.
There is an electronically controlled solenoid that supplys vacuum to the wastegate, make sure all vacuum lines are not broken and sealed correctly.
Start at looking to see if the wastegate rod is moving first. If it is, than your problem is somewhere else, if not start looking at the vacuum sources.
The shaft on the turbo did spin freely correct? It should spin freely as well as no play.
Is the check engine light on?