I used to have a Fiat Uno and wanted faster accelleration.
So I removed the rear seats, spare wheel and jack kit, carpets, front passenger seat, rear plastic speaker supports and belts and mounts and all rear internal panels.
And also only ever filled petrol tank to half full.
This made a noticable difference.
But then I filled it with 6 six inch thick birch ply,80kg of subs, 140kg of batteries, 30kg of flashband, cables amps etc..
It then went a lot slower....