The reason a proper tune is critical is because of air speeds and mixture densities. Longer thinner runners create higher velocity air, but less volume so they are ideal for low end torque because the cylinder will fill more completely with fresh air in the low end. Shorter wider runners are just the opposite. But our ECU is working off of MAP, MAF, and throttle position. So changing even just the runner length means your A/F ratio is no longer ideal even if the TPS signal is the same.
Removing the tumbler flaps is going to change the mixture density at low engine speeds because the air is no longer spinning and won't mix as well, needs more fuel.
So to restate my questions in a previous post, is this manifold designed to improve response with a stock turbo or is it designed to improve flow with a big turbo?