Do K&N pods provide a significant improvement in horsepower?

K&N filter pods (part #RC-1822) pull in more air than the stock airbox does. Combined with the proper jetting, this can help to increase peak horsepower by up to 10% (in other words, less than 3 hp). However, you also lose a bit of low-end drivability in the process, because the pressured air of the box is gone, and the added resonance it provides as well.

Still, this is a recommended upgrade if you do a lot of work on your bike (makes removing/replacing the carbs much easier), and can afford to spend the $$. With newer, more advanced bikes, taking out the airbox would not be a good idea, but with the relatively low-tech engine of the Kawi 250, you can tune it to achieve an improvement over the stock setup.

Also, note that the stock intake is more restrictive than the stock exhaust. This means, if you have to choose one or the other, the intake mod is more effective, not to mention less expensive (about $60-100, instead of $350-400 for a full-system exhaust).

Taking out the old airbox will be a pain in the ass; putting in the pods will take 3 minutes. The K&N's do amplify intake noises (or, rather, do not muffle them like the airbox does). You'll also get a little more underseat storage and a slight drop in weight as a bonus.