OK, just to clarify: You will NOT burn up valves, rings, pistons, gum up valves, or any of that other nonsense. To say that will happen is a flat out lie. You can run an open HEAD (I mean just the head!) if you so desire, with no ill effect. Also, an engine doesn't need backpressure. It's the lack of scavenging that hurts your low end torque.
With that out of the way; Your car will sound horrible and be obnoxiously loud. If that's how you like it, then by all means do what you want! As previously stated, though, it's illegal. Run at your own risk.