A full leather interior, including door cards , seats and b pillar trims weighs in at a hefty 125 kg. Space saver, jack and tools a further 8kg.
Another route is also junking the original air box complete to save 4kg and fitting a dual cone filter in the same place, running a cold feed from the bottom grill and replacing the induction tube, Helmholtz resonator with 2x 76mm i/d 90 degree bend silicone hose and a 45 degree 76mm o/d alloy bend.
That will save a further 3kg and release 4-5 extra bhp and 2-3ft lbs of torque.
Other things you can do to the car is make it as streamlined as possible.
Under trays have some weight but offset it with helping against buffetting and lift at speed.
Removing door mirrors, wiper arms and taping up shut lines on the bonnet, boot and doors etc. This can be done in 30 minutes.
If you are serious and all it is used for is track use. Stiffer rear shocks will help with weight transfer. A Q2 diff will also dramatically improve power put down. All that little lot????
Maybe 1.0 - 1.25 seconds shaved off.