Gymkata, objectively though was there a big diff? Is power jump worth the extra db in sound? How I wish Akarapovic will make exhausts for our baby.
I definitely think it is worth the extra sound. I haven't ridden in an ISF with just the JoeZ exhaust, but according to Jaslapp, the exhaust makes more of the noise than the headers do. The Sikky headers with JoeZ exhaust are only a little louder than with just the JoeZ exhaust, but provide a more savage crackle. It is hard to describe.
I rode around with Jaslapp for about 30 minutes. At first I thought it might be a little loud for daily driving, but we were driving with the windows down. With the windows up, I could definitely live with it and love every minute of driving. Other motorists will definitely know you are there though, as it is much louder outside the car. The sound is absolutely intoxicating.
The important thing is the car isn't that loud in the cruising RPM band (1500-2500). The sweet aural intoxication will spring to life the second you put the petal down though.
As far as a power jump, it felt faster than stock. I was a passenger though, and it is difficult to determine when you aren't driving. Plus I think the meaner sound makes it feel even faster.
The Sikky headers will be my next mod...before an exhaust. Dollar for dollar, I think that is the biggest gain you can make. I probably won't be doing this anytime soon though, as I have to finish building my house first and see how much spare change I have left over.