THIS IS PERSONAL OPINION ONLY:
(Assuming this car is your daily driver and not a drag car)

For the minimal gains you will see from ripping out your interior, it's not worth the trouble. If I remember right, every 100 pounds you take out of the car, you gain maybe a tenth of a second off your quarter mile time. Yay. Do you really care that much about how fast you can leave a redlight? A lot of the stripped interiors I've seen look like poo. There's dirt and rust everywhere, and no one will want to ride with you because your car is so damned loud. Not to mention the possible risk of vehicle profiling from the local 5-0. I'd leave it alone and spend the time on the engine.