In a word- - - -NO! You definitely don't need exhaust gas flowing through the manifold heat tube. The idea is to get hot air to the intake, not exhaust gas. It might be possible to wrap a piece of open-ended steel tubing tightly around the header tube, or possibly braze the tube to the header pipe. Attach a vacuum line to the other end, and draw hot air, not exhaust gas to the intake.
Better idea- - - -use a stock exhaust manifold that's already got a very efficient heat riser- - - -designed by engineers who knew what they were doing in the first place. Headers look cool, but they're virtually worthless except at very high RPM.
Jerry
