You're in luck, no disassembly required.
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240799 - REDUCED AIRFLOW FROM CENTER OUTLETS
Date: 04/30/99
Model year(s): 1999
Description: Reduced airflow from center outlets.
Details: The heater A/C housing on these vehicles is sealed with a foam seal at the instrument panel. This seal can become loose or out of position. If this occurs, an air leak will be present in this location. This will result in reduced airflow from these outlets, be sure to check this seal. This can be accomplished by removing the center outlets and reaching into the opening with your hand. This seal can usually be repositioned without disassembly of the instrument panel.