Hi Andy i have asked all the tuners in my area Collins,Castle performance, turbo systems and even spoken to Ahmed Bajoo and they are all saying that "1". when you do a stage 3 chip change on a RS500 you won't get 330BHP like on normal cosworths you will get around 340 to 360 which means more boost from the turbo, and "2". it needs the wastegate to be enlarged so the turbo doesn't over boost, it doesn't over boost straight away but it creeps up to the point that you won't notice it until it's to late. I have phoned around for a price on getting the turbo uprated ie: 360 thrust bearing ( because mine is on the way out ) new rebuild but as soon as you mention eather RS500 or T4 the price is mad.
I have found a place called the Turbo Centre and they said that they can sort the turbo out for me and machine the wastegate but they would like to find out what size wastegate hole should be machined to and what size penny should be placed in. Thanks for your advice Andy and hopefully i may get an answer soon............ all the best PC