A turbo that isnt internally gated (or you can wire the wastegate shut on it)
An external wastegate
A pipe from the manifold to the external gate
A pipe from the external gate back to the exhaust to keep it all silenced nicely

Thats about it really, boost control shouldnt need a change in hardware but may need the settings changing depending on how you run it.

Ps 400 quid ish as a ballpark I guess