Dulcich had those Stage 6 Chapmans way back in 2002 or so. The reason the TF's would never perform as well as THOSE Chapmans is valve location. Until TF or somebody fixes the valves opening into the cylinder wall then new castings are kind of the answer to a question nobody asked. A set of RPM's ported can match the TF 240's in terms of power--I've done it. J.Rob