BEST AFTERMARKET AIR FILTER FOR HONDA 300EX?
Both are great filters, each has advantages over the other. If you ride a lot of dusty, dirt trails, the K&N will tend to let fine particles by, but you can install an outerwears. Sand is where the K&N is best,the larger particles are easy for it to catch, and it flows a lot of air. Uni filters flow well, also, and are much better at catching the fine dust you get on trail riding, plus with a good quality filter oil, will even repel a little water. Maintenence wise, it take longer to service a K&N, it has to be cleaned, rinsed, and left to air dry, you have to be more careful not to damage the gauze layers it is made of. Foam filters can be dipped or sprayed with cleaners, rinsed, rung out and dried faster, and oiling is easy,spray or soak, then wring it out,and you are ready to go. Having 2 K&N filters,one always ready to use, would make it a lot handier,so the final decision is up to you. With an outerwear, the K&N will flow best,and still be protected, but a quality aftermarket foam flows better than stock, and is a lot easier to maintain. If you pay attention to maintenence, it is hard to go wrong with either. The only big difference is price, you will tend to pay a bit more for the K&N.
The full power kit is the K&N filter and a jet/needle kit, made to get the most out of the flow characteristics of the K&N filter. Together, it makes a noticeable difference, as you will need to rejet due to the extra flow of the K&N anyway.