http://www.xt660.com/showthread.php?t=19483

So maybe a little bit more facts from someone who has S3 filter, instead of some graphs, advertisement or speculations of someone who don't even wants to try one...

Before i go to Stage3 i had on my bike K&N and snorkel cut out + Kev mod.
This setup was brilliant, however i decide to give a try and ordered stage 3.

Now my observations:

+ bike is reving much quicker now. I was hitting rev limiter on first three gears during first ride with DNA S3 fitted as i didn't expect engine to rev so quickly.

+ above off course means quicker acceleration (or at least impression as i didn't measure)

+ maximum speed improve slightly. Biggest improvement is after reaching 85mph... with stage 3 filter when overtaking on the motorway she was still stretching arms when 95mph on the clock (!!!) she is really going strong up to 102, and then slowly gets to 105 when with stage two she was going strong up to 90, and then slowly to 102 (this is off course indicated speed)
She is faster now than GS500 on the road. Pretty good for enduro, eh? :-)

+ very small (almost unnoticeable if you know what you doing with throttle) lose in torque in mid range.


- Power wheelies (just throttle without clutch shot)on second gear still impossible. First gear wheelies though danger as she is going vertical quick...i mean qiuck :)

- quick reving and throttle response make you think you riding 450cc instead 660... if someone likes big thumpers like i do this might be downside. But to be honest speed and responsiveness made up for this.

All in all - if you ride a lot on tarmac, and occasionally go for some green lanes i recommend this. I won't comment on heavy offroad, as i haven't done one yet but i can see it might struggle on type of roads like in uberthumper link :-)
But for some easy green lanes its safe.