AT THE Paris Motor Show in October 1948, Automobiles Citroen introduced an ungainly little vehicle powered by an air-cooled flat-twin 372 cc motor developing a whopping nine horsepower. Called the 2CV and shaped like a pram, it caused a stir with its unusual appearance, its ultra-economical character and its potential for varied use. From October 1949 to the end of 1984, 3,662,903 examples of the 2CV and its light commercial version were produced. Again at the Paris show of 1955, the French manufacturer unveiled the revolutionary DS19 sedan, remarkable not only for its aerodynamic shape but also for its many technical innovations, including something called hydropneumatic suspension. By the end of the first day of the show, 12,000 had been ordered. Citroen has always marched to its own drum. Its design and engineering concepts, addressing alternative principles and issues, have produced a long line of cars with distinctive character and appeal. They are either loved or scorned, leaving little room for indifference. It is therefore in keeping that there are few fence-sitters when it comes to the Citroen XM. Suggesting the executive saloon that won the European Car of the Year award in 1990 is a ''little'' unusual is somewhat akin to noting Charles De Gaulle's nosewas a ''little'' large. Introduced in Hong Kong in 1992, the front-wheel-drive XM was designed for Citroen by Italy's Bertone and was a bold attempt to ensure its flagship model advanced competitively into the '90s while retaining a high degree of individuality. From a styling perspective, this was done in traditional Citroen fashion. Though thoroughly modern with its aggressive leading sections, the rear treatment, with the odd-shaped quarter window and abbreviated tail suggests a strong influence from the days of the distinctive DS. Coming or going, the XM is not likely to be mistaken for any other car. It is sold by Concord Limited in Hong Kong in two trims. From the outside, the top-of-the-line level four listed at $399,000 differs from our test vehicle, the level three which costs $375,000, only in that it has styled alloy wheels and a braking indicator light in the rear window. Occupants are given not only large, comfortable seats, but a truly unprecedented amount of space to stretch out in. An optional $15,000 leather interior is at home with other luxury and convenience features, such as powered seats and automatic seven-speed air-conditioning. The level four package includes wood trim on the dashboard, centre console and doors, a sophisticated audio system with remote controls on the steering-wheel and an unusual electrically-powered, height-adjustable centre armrest. Also peculiar is a second glass panel beneath the rear window, said to enhance cabin insulation. ''Intelligent'' hydractive suspension, a computer-controlled active-ride version of Citroen's original hydropneumatic system, is one of the XM's most unique technical aspects. Each wheel is independently suspended, using gas and liquid to replace conventional springs and shock absorbers. Reacting to several sensors gathering information on driving conditions, the system automatically dictates the appropriate response from the suspension. The sensitivity of these responses can be controlled by selecting a normal or sport setting. An additional anomaly of this set-up is its ability to raise and lower the entire chassis by 30 centimetres by sliding a lever on the console. This function, Citroen explains, is useful for clearing obstacles, negotiating rough tracks and changing wheels. It is also entertaining as an eyebrow-raiser while waiting at stoplights. The XM's three-litre V6 engine delivers 170 horsepower through a four-speed automatic transmission. Despite its size, the saloon feels responsive and agile. There is a certain amount of re-learning to be done when driving the XM at speed. The hybrid suspension places emphasis on not only a smooth ride, but also the ability to keep the entire platform absolutely level. This objective is accomplished with unerring efficiency, but the usual feedback associated with knowing when limits are being approached are absent, replaced by a sinking feeling of detachment once the threshold has been crossed. In the end, the best solution is simply to back off and enjoy the more sedate yet supremely comfortable role for which the XM was intended.