So let's recap...

I have a wet kit... I said that you have to be careful of "pooling" in your intake manifold. This would only be relevant to people with a wet kit since dry kits only dispearse nitrous.

Intake manifolds are made to distribute air not fuel...I know many of cars who have had thier N20 backfire in their intake manifold because of "Pooling" including my own.

So now let's see can nitrous pool in your intake manifold and cause a backfire? Does that have anything to do with timing or worn valves?