Some models had six-cylinder engines, optionally with electronic fuel injection, borrowed from the larger Crown. For the Japanese market, all Japanese models engines were upgraded with Toyota's TTC-C technology to comply with the Japanese Governments Clean Air Act of 1975. In late October 1977 the 3T-U engine was upgraded to pass the 1978 emissions standards with the aid of a lean-burn design. Four-cylinder engines were mostly reserved for cars intended for commercial usage. The X30-series chassis numbers were the original codes for the third-generation Mark II, with X40 numbers being gradually introduced about halfway through the life of the model for cars that could pass the new, stricter 1978 emissions rules. In October 1979 a diesel-engined Mark II went on sale, a first for the badge. In 1998, Toyota released a car called Progrès. The Progrès front end looks somewhat like an updated version of the X30/X40 series sedan. For instance, both of them feature a combination of round and squared lighting. The grille and bonnet also has similar shapes, size, and lines. The Toyota Chaser was released in 1977 as a competitor to the Nissan Skyline sedan. The original Chaser was a rebadged Mark II with a lightly differing front and rear treatment, of a higher class than the Mark II. Later generations received more differentiated styling. The idea of the Chaser was to offer a sportier version of the Mark II and sold at a different Japanese Toyota dealership called "Toyota Auto Store", often with more powerful engines and different suspension setups. The Corona Mark II was renamed the Toyota Cressida for export markets, and the name Cressida was not used in Japan. Production started in December 1976. The name Mark II was previously identified with the North American Continental Mark II which first appeared in 1956 and the term "Mark" is still associated with Lincoln Motor Company products. It was Toyota's largest sedan and wagon range offered in North America, while the personal luxury coupé wasn't offered. In New Zealand, a two-litre four-cylinder sedan version replaced the six-cylinder Crown in local assembly after the 1970s oil crises prompted the government to impose a 60% sales tax on cars with engines larger than two litres. A few fully built up Crowns were subsequently imported. In other markets, the larger Toyota Crown also remained available. The name "Cressida" derives from the lead character in William Shakespeare's play "Troilus and Cressida", inspired by Cressida, a female Trojan character.