im not really sure whether its actually worthwhile on a road car, i have had the back seats and all the boot carpet out of mine, it felt quicker but then it was noisier so most of it was probably just in my head, last time i had it out i put it all back within an hour, it didnt feel right to me. the extra noise isnt worth the possible gain, plus i found i simply couldnt make myself drive sensibly with no interior, probably just me but with the extra noise and a bucket seat all common sense went out the window! its not even a nice noise in mine, the exhaust is more audible which i didnt mind but the road noise soon gets boring.
on a track car its worth it, when you will be putting your foot down for such a short time it isnt worthwhile imo, plus the car is effectively useless without the interior, it becomes a 2 seater in which you cant leave anything even slightly valueable because theres no parcel shelf and rear seat to hide everything, not something you would want to leave in a car park, sounds like a good idea until you do it, then you will hate it.