Abstract: An exhaust gas re-induction apparatus and system. The exhaust gas re-induction apparatus is coupled to an exhaust system or catalytic converter of an engine. The exhaust gas re-induction apparatus includes an oxygen sensor substitute apparatus having an exhaust gas diffusion chamber disposed therein, and an exhaust gas interface housing to receive the oxygen sensor substitute apparatus. A recirculation conduit connects the exhaust gas re-induction apparatus to an air inlet of an engine. The oxygen sensor substitute apparatus includes a coupling section to attach the oxygen sensor substitute apparatus in place of an oxygen sensor apparatus. The oxygen sensor substitute apparatus also includes an exhaust gas dispersion section having a plurality of orifices for dispersing exhaust gas. The exhaust gas re-induction apparatus and the recirculation conduit have always-open passages in which the exhaust gas is recirculated to the engine at different rates depending essentially on the operating speed of the engine.