I had one on my 94 Z/28, car was quiet as hell when close and slowed the performance down a ton but when you open the cutout it made quite a difference, caught many a ricer on the street by surprise. Just get a good brand the cheapo ones leak.
I have installed a couple sets of electric cut outs since I do custom exhaust. I have manual exhaust dumps on my own car. You have to remove 3 bolts to uncap the exhaust.