I've just installed the Arqray Twin Muffler exhaust. Its a Super Stock SCCA legal exhaust because it doesn't require cutting or modifying the body to fit. The install was pretty easy, about 2 hours. Out of the box it sounds deeper. The butt dyno isn't sensitive enough to measure, however from dyno graphs I've seen it's good for 4whp. The main reason I got it was because it's lighter than that stock exhaust, but the sound is a big plus, it's actually very nice, not too loud. For a good discussion thread on installing any aftermarket exhaust on the Lotus Elise.arqray exhaust sound
