On my '99 there's a threaded end and white plastic part right above the gas pedal. That controls the flap that shuts off air flow to the floor when you select defrost only. It might be different on a '00-'01.

I've had to adjust it twice so far 'cuz I was getting too much air on the floor when I wanted it all up top. I separate the two parts and select defrost only, then move the flap arm to close it tight, then snap the threaded metal part into the groove in the white plastic part. The threads are there to keep it from sliding out of position. Then it closes tight when I select defrost.

I hope that's what you're talking about.

Mark