WE don't have Miata's here but iv'e had a bmw e 30 for street racing (2 L 6cyl) must admit fast and handled well but too costly to modify
I removed the rear seats,spare wheel,stereo,all the sound reduction paddingand some of the panels replaced with plastic ones ,fitted an induction and a de cat zorst oh yea a remap to i was running just under 200 bhp at the flywheel through 205 , 50 , 15 pirrellis