I have a UK made turbo that cosworth use on their rally car builds, t04e 500hp rated. on the current 2.0 with twisted setup, and headers, it spools circa 4500 and makes good power 4800 and above (240kw). 1st gear it doesn't do much until 5500rpm. I realise I could change to a more appropriate turbo for a 2.0 and get the same/better result, but the turbo setup is already done, and my cast piston block is getting old now and could do with a replacement any way.
This is also why I want to use v4 heads, as I already have the manifold fuel rail injectors and computer to suit.