I just installed the mid-pipe after about a week or so of having the dual SS tip only. I found that the mid-pipe definitely quieted and mellowed the exhaust down. Before, without the mid-pipe, there was definitely the droning mid cabin and the exhaust growl was much more pronounced. It was louder while blipping the throttle. Very drony from about 2500-3500rpm mid-throttle, quieter till about 4500 and then the scream at higher rpm's. After the install, the drone was gone at the lower rpm's and the volume basically shifted rearward. It seems to be "loud" only when you really want it to be (WOT). Still noticeable volume but I think its much easier to live with.
One other thing is that it seems to "pop and gurgle" more on deceleration as well as in between shifts with them mid-pipe on.
As for power gains, don't know if its just the "volume placebo". Seems to rev more freely and pull a bit harder.
[This message has been edited by Arnie (edited February 09, 2001).]