Saying a B6T cant spool a GN turbo is like saying a ford 2.3 cant spin a Holset. Its not all just which motor it is, or which turbo.
Yet a friend of mine gets 26 psi out of an HX35 by 3000 rpm, with a fairly stock 2.3 ford, in the 350-400hp range.
I run a "small" T3 on my BPT, .42/.48 from a Saab, 45 or 50 trim. I get 15 psi around 3000-3500. I believe that turbo is good for around 400 cfm.