Between the price of gasoline and diesel fuel and the environmentalists who expect all internal
combustion engines to emit nothing other than flowers and perfume from the exhaust pipe, engine modifications have
taken a hit. Fewer automobile enthusiasts seem to be making major, hard-core upgrades to their gasoline and diesel
engines. That’s really too bad because most engine modifications that increase horsepower usually also increase the
efficiency of the engine, and therefore, once the novelty of the added performance has worn off and the driver
settles back into a normal driving mode, the fuel economy delivered by the modified engine increases.