shared the same drive train and engine as in the previous year (1973), based on the Corvette L82 special high-performance engine (the Z28 would re-emerge in 1977 as its own model and no longer a RPO). Camaro sales increased to over 150,000 units, of which 13,802 were Z28s (the highest 2nd-generation Z28 production to this time) despite the energy crisis fueled by the Arab Oil Embargo. Two ponycar competitors were repositioned in the marketplace this year. Ford downsized the Mustang to an all new 1974 Ford Mustang II subcompact based on the Pinto that was designed for an era of high gas prices and fuel shortages resulting in 385,993 units produced for the model year. Mercury upsized the Cougar to an intermediate-sized personal luxury car to compete with the Chevrolet Monte Carlo and Pontiac Grand Prix. Other changes included Chrysler Corporation discontinuing the Plymouth Barracuda and Dodge Challenger during the course of the 1974 model year. Likewise, 1974 was the final year of the AMC Javelin, but a sporty AMX model would be reintroduced in 1978. 1975 For 1975, a catalytic converter was added to the exhaust system of all US-market GM passenger cars, including the Camaro. The "Air Injection Reactor" secondary air injection system was still present. The catalytic emission control system was more efficient at reducing emissions than the previous non-catalytic system, and allowed engines to be retuned for improved drivability and fuel economy. The catalytic converter and GM High Energy electronic ignition were advertised among the components of "Chevrolet's new Efficiency System" which was promoted to offer other benefits to owners of 1975 models versus comparable 1974 models that included extended maintenance intervals from 6,000 to for oil/filter changes and spark plugs that lasted up to compared to on 1974 models. The Z28 option was discontinued for 1975 despite an increase in sales to over 13,000 units in 1974. Optional engines continued to reflect the impact of emissions. Two 350 cid (5.7 L) V8s produced 145 hp (108 kW) and 155 hp (116 kW) (Horsepower losses can seem a bit exaggerated compared to earlier cars, however, their power ratings were now net as opposed to the prior gross ratings. SAE net power ratings (used since 1972) were taken from the engine crankshaft as before, but now all accessories had to be attached and operating, and all emissions equipment and a full production exhaust system had to be