An herbal formulation for prevention and treatment of Diabetes and associated complications comprising extracts from selected Indian medicinal herbs. At least part of at least one of the side surfaces is processed to prevent the stripe-shaped waveguide from functioning as a Fabry-Perot resonator in the width direction. The controller is configured to change or maintain engine operation based on the one or more signals compared to the threshold limits, and to change or maintain an engine fuel supply to control specific fuel consumption of at least one of the first and second fuels and to achieve values for the one or more signals in a determined range relative to the threshold limits.