Some bold claims for the VWR one. Up to +9% peak power and turbo spool reduced by 500rpm. The latter I'm a little skeptical of personally, given it's the turbine wheel / housing that has the biggest influence on spool up
They don't state under what conditions and mechanical spec you get those gains. For example, do you need a full exhaust to see those improvements? And at what boost pressure and rpm do you see that +9% increase in hp?
£450 is a lot to take a punt on it, based on vague sales pitching.
I suspect VW Racing saw those gains on their own racing car, which runs shed loads of boost, full exhaust etc etc. I reckon a mild stage 1 tune with just a DP would probably see about +5% because at 1.4-1.5 bar, the turbo isn't struggling that badly to get air in. So around 15hp for £450? I don't really see that as a good £ per hp investment personally, but that's only because that kind of money is almost a VWR spring a damper set, which would give more profound and noticeable gains from the get go :)