I've read a lot about it on some import forums and the feedback seems very positive. Several people who have knock sensors logged the difference between how much timing was pulled with 93 or 94 and with one or two cans of torco added, and it was significant. But no one seems to really know exactly what's in it or how it works, other than I think it does have some MMT in it. To raise octane as much as they claim with the volume of additive they're using would make the torco very, very high octane, and I know some people with backgrounds in that area have been very skeptical. But the bottom line is it seems to work, and the only apparent side effect is some reddish residue on your plugs.