You cannot compare pre-turbo exhaust flow and post-head exhaust flow when supercharged. The turbo becomes your biggest restriction in the exhaust, making plog/stock manifolds not an issue, and people have made close to or more than 400whp on 2 stock manifolds and a z3/similar crossover. You don't need good flow before the turbo, you are just building pressure to spin the turbo, so it doesn't matter nearly as much as it does when supercharged if it flows well. Just needs to get pressure to the turbo.
Two COMPLETELY different animals.
