Pontiac 1999 Firebird - Manual (Page 12)

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Reclining Front Seatbacks
To adjust the seatback, lift the lever on the outer side of
the seat. Release the lever to lock the seatback where
you want it. Pull up on the lever and the seat will go to
its original upright position.
If you have fully articulating sport seats, your recliner
lever looks like this.