I have no problem with my torque up to 5k rpms. They do give up a little, but not as much as a big set of cams will. You're not going to find a lot of other manifold review besides the Greddy (and copies.com.cn) because the others are twice as expensive. I wouldn't look at a Greddy IM becoming useful until you've got a 2871r or bigger, and cams.