I know this topic has probably been done to death, so I apologise for bringing it up again. However I just would like an answer to a couple of questions regarding boost controller/Dawes valve install. The car in question is a 2008 CRD ZD30 (stock aside from a provent 200, current max boost is around 14psi and very erratic at low rpm)

Do you have to install a needle valve, as well as the boost controller?

What are the advantages of using the needle valve? (Is it just to do with a more linear boost curve?)

To run a Dawes/needle system, does the EGR need to be blocked? Or can I leave it and simply install the Dawes/needle valves?

Thanks heaps in advance! 👍