As far as the "always under boost" thing o a supercharger:
Jackson Racing's (I know - no plans for the Protege's) charger for he Miata has a vacuum-activated bypass for the unit - under normal driving, the airflow circumvents the charger "spool", with most of the air going direct to the throttle body, for better longevity, fuel economy, and less strain on the engine and charger. Under heavier throttle, the vacuum valve opens, sending the intake charge through the charger for the forced induction. Sounds like a nice design, but I've heard at least one person say that the quality and fitment for he Miata isn't as good as it could be, especially for the price.
Still, I used to drool over them when I had my '93.