Wastegate restrictor to stop boost spike - Caldina

[Lac]

So i just got the car re - tuned and it came up as 150kw atw. (relates to GTT dyno post)
One thing happened though, on the dyno there was no boost spike but on the road tests it would always for a split second spike hard and then drop off. (common problem)

My mechanic ended up putting a wastegate restrictor on (not sure exactly what he did), he said it was due to the valve not opening up quick enough on the wastegate, causing to spike.
Has any one else done this on their caldina? restrictor ? Considering how much people have talked about boost spike on the caldina...
Note im running a EBC.

I found an interesting article about it here -
http://autospeed.com.au/cms/title_Shoot ... ticle.html