valves will be fine, tons of race cars run straight pipe, back pressure is not required. but that will take this thread off on a tangent. i know when my exhaust came off and i ran straight pipe it was disgusting, and stupidly loud, so i slipped a glass pack i had laying around the garage on it and it toned it right up. still loud and aggressive. magnaflow is a little more tone downed and clean, same with flowmaster. to me flowmaster just sounds a little more like a car with pnemonia vs magnaflow. youtube for samples to narrow your taste if you decide to put a muffler on it

 

Are you sure about that?