Cubes makes more low end torque but not necessarily more hp. I promise you can make just as much power or more power with a 231ci and a 70mm than you can with a 280ci and a 70mm. The difference is the 280ci will come up much faster and won't need the rpm or boost to get a decent 60'. People do have monster turbine sides on small engines and run 8's. Supra comes to mind And they also need nitrous to spool them. The reason you don't see it everywhere is because nitrous isn't allowed on boosted combo's. Take the nitrous off of yours and see how well it works. If you had to race without nitrous you'd be forced to go back to a smaller turbo and you would slow down. I have seen a car drop backpressure and instantly need an extra 200pph of fuel. 6 second drag car. So yes that is where your gains are at. It's not magic engine design....it's all about that back pressure.