Ive never entered a DV debate, so let this be the first lol

If they were needed, Ford would have fitted them to the MFI'd turbos. If the 'chatter' was seriously dangerous to the turbo, no-one would do it......

Now to me, a dump valve is purely a tool to allow knowledge to others that the car is a true turbo and not an xr3i with an rs bonnet and kit.... thats about it. I havent got one fitted any more (but i must also say that I do actually miss the noise lol)