As Steve has allready said, throttle bodies on a turbo engine will give you more throttle response when you rev the car at idle for example, or when blipping the throttle during down changes etc, but it will make no difference at all to the turbo response, so when you change gear, you'll still be waiting for the turbo to re-spool exactly as it did with a single throttle.

Also again exactly as Steve has allready mentioned, a throttle body turbo setup cannot run soley as speed density. That means you cannot map your fuel requirement purely based on MAP V RPM. It requires significant throttle angle V rpm V map correction. My personal preference in this matter is using Pectel T6 with its multimap throttle angle correction maps.

Hope that helps,