For a dump valve... I would recommend the GFB adjustable BOV
http://www.scoobyparts.com/performance/gfb-tuning-products/gfb-respons-tms-bov
You can choose between full recirc, full atmo or any combination inbetween. Going full atmo has chances of causing issues, mainly lumpiness between gear changes due to the engine running rich because you've dumped all the air. I personally use this BOV and I have it set to almost 100% atmo. I found after a while of having it I was getting some lumpy gear changes, so I tweaked it a little so a small amount of air would recirc and it completely resolved the problem. The spring is adjustable as well so if you modify or rempa for extra boost, you can tighten the spring so it doesn't open too easily. A very versatile BOV.