Yeah, for drag racing, its all about how far you want to go. Some people like to race with full interior/stereo/gas tank so their times seem more impressive... for bragging rights, i guess. But the more weight you can remove from the car, the faster it will be. I've seen people gut their interior, remove engine accessories, remove bumper braces, A/C, stereo, unnecessary wiring... For autocross, you can't really go any further than removing your sub/amp and your spare tire, unless youre in prepared class, or SM for some items.