As stated they are not made for a full on nitrous backfire, however they do a fine job on a big plenum intake on choke less cold starts or until one gets the timing/carbs correct.

They do work, the self resetting part is 90% true so put them where you can reach them as the rubber O ring can get moved out of place.

I dont think the few brief cranking coughs back through the intake that did release through the plates would of been strong enough to hurt a carb.

But if it saves things one time, they were worth the cost and install time.

I like the plastic bolt idea on a track car that calls for it.