I used them and they sucked. I got mine from Quicktime performance and they would not shut all the way which caused a real bad leak and sounded horrible.
were those the manual ones or the electric, my buddy has a set on his cobra and yes they were around 400, but worth it when you wanna run open headers at the track !
DMH has the best ones out there. They come with a 4 year warranty and when the cutout is fully opened or close the motor shuts off even if you are still pushing the button.