Boy I hope I can prove myself wrong, but I have done back to back runs with my Q4/powerbomb combo and my stock exhaust (with exup locked open), and they seem the same. Just riding around, the FMF sounds better, and I'd say it seems more responsive, but I think it's all in my head. (sounds better = faster, right??) I spent hours cracking wheelies with both pipes, and the bike responds the same (yes this is subjective). My other more databased test is a full throttle acceleration up a long hill near my house. I hit a certain spot on the hill at 50mph in 5th gear, and go full throttle to another spot. I hit the same speed in the same spot with either pipe. Acually, the stock pipe got me an extra 1mph sometimes. I have done the airbox flapper mod, EXUP sub, and AIS removal. I have an FMF Programmer and I've used the stock settings as well as 333888. I will say that those mods made a difference (not sure how much to attribute to each). I'm in the process of hooking up an Innovate LM2 data logger with a wideband o2 sensor. I will log RPM, throttle position, and the o2 sensor reading. This will allow me to plot data from my hill climbs. Anyone have real data saying that the Q4 is better than stock?