[budomove]

2 things are possible.

They updated the battery condition monitor and motor control module in 2002 to increase battery life, but some say the change hurt mpg. dunno why the epa rating changed twice though.

They added a 3rd o2 sensor in '02, downstream of the 2nd cat.
Its purpose was to differentiate b/w failure of the 1st cat, and that of the 2nd.
On 00-01 models, the o2 sensor downstream of the 1st cat was the only indicator of cat failure, and you must still buy both cats when this happens, because there is no way to know whether one or both have gone bad. I don't know if the 3rd o2 sensor somehow has an effect on mpg.

prolly the bcm/mcm upgrade, and potentially the ecm upgrade they did had some effect, although it was designed to fix the faulty cat failure codes that resulted in many unneccesary cat replacements, that have since been reimbursed.

frank