This pipe is awesome. Replaced my stock pipe on my 07 KX 450f. As soon as I started the bike, on the stand, it seemed to run better and idle better, even on the stand! It had a better throttle response at the lowest rpm. Crisper than ever. Then I rode it, more power and quicker throttle response at the low to mid rpm's. And excellent power everywhere through the rpm range. Highly recommended. Get out and ride!