Velocity stacks are not a gimmick at all. There is very good science to tuning an intake. Many racers will tell you that the center of the carburetor piston should be X amount of from the valve. My old Triumph was said to need the center of the AMAL carb to be 7" or so from the intake valve. The manufacturer could not make the bike like that, however racers didn't care if their custom intakes stuck the carbs out of the fram, that's why on old race bikes you see them dangling out the sides. A tuned stack can replicate that intake by leaving the carb in place. It's not as good as having the correct intake manifold, but it is a good compromise. They really tune the low end portion of the throttle, the first 1/4.
TPO posts dyno runs of their results, how can you call that a gimmick?
The prices are very high as your battery box gets effed doing the conversion. You get a new battery box and new coil holders as the bottom airbox serves as these devices on your machine, I believe you have an S2R800. You need to verify that the kits come with everything, many kits will just assume you are a custom builder and figured out your own trick.
Get a copy of the LT Snyder repair handbook for your bike as he has a great right up of how to do the conversion and why to do it, and why not to do it.
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