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as far as intake manifolds, a jmf or a magnus are the most commonly used. i have a jmf race smim on my car. for a nice equal length exhaust manifold, theres shearer, straight line specialties, or punishment racing. those three are all good, shearer is the most expensive out of the three. like tonus said intake manifold, exhaust manifold, and some cams would improve the spoolup on a stock motor with a bigger turbo. what do you have for fuel, what size injectors, pump, fuel management?
I don't really think a bigger intake manifold and bigger cams IMPROVE spool time, I would argue that they make it worse, but give you way more power up top. A stock intake manifold is gonna give you the most low-end power, it just depends on what you want to do with the car. If you want to drag race it, and you're only concerned with peak power, then get a bigger intake manifold, big cams, and a HUGE turbo. If you want something that's streetable then go with a more mild setup. I'm a fan of the JMFab street plenum intake manifold, HKS 272's, and a stock throttle body. This is a great street setup when used in conjunction with a GT35R and an equal-length header.