Hmm I had a little think about this and I think that response would be just about identical as long as the intercooler is correctly sized and the bov is working as it should. Way less lag too I'm thinking approx stock motor lag. So the crossover between low boost and high boost would need to be fiddled with, but wouldn't be too difficult.
see, i'd think it'd reduce the response due to twice the drag through the turbo and all the extra pipe work.
also what are the intake temps going to do being double compressed? e85 needed? methonol even?
ive always wanted to know what intake temps would be like compared to a normal set up, never looked into it but i would have thought it would be much much higher