I just installed the FMF Q4 in Stainless Slip On. It was around $400 with 2nd Day Shipping. Install was a breeze and I think the stock system is about 2 lbs heavier, maybe more. I didn't weigh either system. So I am down about 4 lbs with the AIS and Muffler. On the test fire, it sounded great, but I haven't had a chance to ride it yet. I installed the 06 GYTR AIS Removal kit and it was the best mod I made on this bike so far. It really woke it up and the off idle bog is gone. I ended up fabricating my own block off plate out of aluminum. Great Bike So Far!