I recently installed an OS V Spec .21 in my buggy. Unreal is all I can say. I am also running the OS 2000 header, and OS 2060 tuned pipe. Great combo, moderately priced in comparison to others. I dont have to touch the tune all day. It fires up easily. If 25 guys reply to this thread, you'll get 25 answers. I dont know of any engines that are really bad so to speak. Every engine has its good points and bad points. I have yet to see any bad points for the OS V Spec.