Well it all depends on tunning as well. There are 6 of us in a group that ride every week and we all have 450's with different types of exhaust. I have big gun race(loud as hell) series full system. Other are hmf full pipe, sparks full system, gtyr full system, and 2 modded stock exhaust systems. In the trails no one is faster than the other from exhaust it's about the rider. Hill climbing in the trails the full exhaust bikes perform better than the stock modded ones do. Now when it comes to full drag on concrete, stock modded dosen't even come close. Gtyr comes in next but right on the hmf's bumber. Mine with the big gun(before custom intake) with the stock filter and the curtis sparks with the sparks filter are neck in neck it depends on who hits the gas first on roll ons. Now with my custom intake with stock filter I can pull a quad from second to third but from fourth to fifth, I pull another 2 and a half. Hmf performs great as so does sparks and big gun. To say esr would smoke all these pipes is crazy. Pipes for these bikes can only get so good. It's all about set up and rider. If people belive everything they read about power from pipes then I wouldn't dyno your bike stock than bolt your pipe on and make another pull cause your not going to see 10-15 horse from a pipe alone at the tire like advertised. These pipe dealers are just like car sells man, tell you what you want to hear that makes you feel good so you will buy :lol
