Yeah - had one on mine with various configurations. With std. zorst, it made very little difference other than increased fuel consumption. With Y-piece and Remus, it could be tuned to turn the bike into a torque monster with little detrimental effect on consumption. It had no effect on top-end power that I could discern, however.
After I took it off and sold it, I tried the 'Steptoe link' for the cat-code plug (connecting 30 & 87A) and found that this gave almost as much mid-range (with a Y-piece + std. can) as the Techlusion/Remus setup. It's an expensive way to gain very little, IMO.