Individual throttle bodies on a turbo charged motor are pointless, can result in no benefit in your application, and can result in power losses, depending on how they would be implemented. The correct engineering for your app. is tubular runners going to a plenum. The throttle, (singular), can...
the situation is a little worse than you imagine; at closed throttle over-run your efi car is injecting fuel. It`s maint aining the 14.7 A.F.ratio with it`s O2 sensor and closed loop adjustments; this is to keep the CAT alive. The rationale for mpg is that you spend very little time in this...