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Throttle body spacers in EFI engines really don't help anywhere near as much as the claims. I doubt you'd even notice any improvement at all.
Carb spacers when vehicles had carbs actually made a lot of sense and were effective, because the carb would insert fuel into the airstream in "suspension", and having the spacer allowed for the airflow into the intake to make a slightly less sharp turn, thus keeping the fuel suspended in the air before getting sucked into one of the intake runners.