Under 650 a single over twins or if you want faster spooling or just WANT them, then just do it!! But.... If you want BIG numbers you will have spooling just like a big single but top end well above a big single. It just takes 1 extra turbo + 1 extra waste gate + 1 extra blow off valve. If you can fabricate then thats good for you. But if your having someone doing the work for you it starts adding up. You still need to fabricate the same components just adding the exta items into the mix. The turbo technology of today has brought us fast spooling singles that can perform just as good as twins from 15 years ago and pull just as hard. It boils down to fabrication required, performance and specific wants.
