Does anyone know where i can get a bac valve for 91 n/a......and how much those things cost...... or is it better to just unplug the thing???

 

I don't know what your plans are, but personally I'd keep one on my car. I'd imagine used you wouldn't pay all that much. You could go to the forum's Buy/Sell section. Ebay. If you want one new it'll likely cost a substantial amount (as all Mazda parts do). You could try Victoria British, Mazdatrix, Mazdaformance, your local mazda dealer.