you are forgettin that the gas mileage standards are chaning all the time and they have to meet them. they also use different computer systems. odb1 and 2. so they aren’t infact unchanged in that time period.
" the Mercury Grand Marquis and Ford Crown Victoria, were curvaceously reshaped for the 1992 model year. In addition to getting new skin, the Grand Marquis was now powered by Ford’s 4.6-liter overhead-cam V8. It provided 190 horsepower, pumped to 210 with the optional dual-exhaust system" so the 4.6 was 190 hp in 92…and stayed like that for a few years…