OVER the last decade, Cadillac has found it harder and harder to attract the "young affluents" who make up the bulk of buyers for European and Japanese imports like BMW, Lexus, and Infiniti."These people," says Peter Levin, Cadillac's marketing manager, "really aren't thinking about Cadillac." Come this fall, Mr. Levin and other Cadillac executives are hoping to change that mind-set with the introduction of what some are calling Cadillac's most important new products in decades. Unlike the boxy, highly plush Caddys of the past, the new Eldorado and Seville are taut and sleekly aerodynamic. In looks, ride, and handling they have a lot more in common with imports like the Lexus LS400 than the Cadillac models they replace. In a recent review, William Jeanes, editor of Car & Driver magazine, suggested the new Seville four-door "does not look, feel, ride or handle like any Cadillac we've ever driven." With the 1992 Eldorado and Seville winning such positive reviews, Levin says Cadillac can "alter the belief among [affluent baby boomers] that Cadillac doesn't make a car for them." Perhaps, but the division of General Motors Corporation does have a lot of negative images to overcome before it can stand shoulder-to-shoulder with its well-perceived import competition. The lack of interest among baby boomers - and the loss of many older former buyers - is the result of a succession of problems that plagued Cadillac during the 1970s and much of the 1980s. Among other things, a series of faulty engines left customers stranded and steaming. In 1985, Cadillac introduced new and significantly downsized versions of the Seville and Eldorado designed to appeal to buyers worried about rising fuel prices. But potential customers complained that the vehicles looked too much like the less-expensive products sold by other GM divisions. To make matters worse, there were intolerable quality problems. As a result, Seville and Eldorado sales slumped to less than half their early '80s average of 70,000 to 80,000 units a year. Cadillac made some modest styling changes in 1989 that helped improve customer acceptance, but even so, the two vehicles will account for about 41,000 units of volume through the end of the 1991 model year. John Grettenberger, Cadillac's general manager, says his target is at least 60,000 units in 1992, but "I won't be happy unless we can beat that." To win over the young affluents so essential to that plan, he says it will take more than just a new product. It will take an entirely new approach to selling the cars, as well. The vast bulk of Cadillac's advertising budget for the fall will be aimed at potential Eldorado and Seville buyers. Cadillac will drop the emphasis on affluent lifestyles. Instead, the spots will acknowledge the fact that young affluents seldom consider a Cadillac when choosing a luxury car. In one TV spot, for example, a woman in her mid-30s voices her concern that "European sedans and coupes are built to a higher standard." By emphasizing the technology, safety, design, ride, and handling of the cars, the TV spots and print ads hope to explain just why such a buyer should now take Cadillac seriously. As part of its marketing plan for the new cars, Cadillac has been developing a list of 11,000 likely buyers gleaned from those who attended recent auto shows around the country. Significantly, those who expressed a strong interest in the redesigned Seville are better-educated, wealthier, and younger than Cadillac's current buyer. Two-thirds were under 49, or nearly 15 years younger than today's average buyer. Just as important, says sales manager Peter Gerosa, of the 11,000 prospects, "only 32 percent were current Cadillac owners. That's wonderful from our aspect." Cadillac will also use price as a selling point. The base model Seville will carry a sticker price of $34,975, or roughly $5000 less than the hot-selling Lexus LS400. The base Eldorado will cost $32,470. If the new Seville and Eldorado meet their targets, that should go a long way towards restoring the huge volume-leadership Cadillac held in years past. As recently as the 1984 model-year, the division sold 327,587 cars. Last year volume was just 256,763, and Mr. Grettenberger says that should slip to just 225,000 for 1991, as a result of the recession and the new luxury tax. But with the Seville and Eldorado receiving such a strong initial response, he believes they'll help boost Cadillac's overall volume by 11 percent in 1992. The success or failure of the two new models will likely determine the division's longer-term direction and image, Grettenberger says.