[fminicooper]

Hi,
I have been tracking my car for more than two years with several hundred miles on her. I drive in Texas (MSR Houston, Cresson, COTA, EagleCanyon, San Marcos)

My objective is to prioritize track time and improve my driving skills. My main expenses are track fee/brakes/tires. In order to do that (with my limited budget) I have been modifying the car for reliability and performance, barely no cosmetic mods.
I do all my work myself but alignment.

Car is in very good condition (27K miles), using for weekends and track events (no Autox). I love it and love it more after tracking it.

I started tracking in OEM configuration, latter modifying it base on above criteria.

Finally this is what I have.

Engine: NA, OFT Tuned E85, Oil Cooler, Baffle Pan Blue Moon, Decatted, Verus Hood Vents.
Brakes: Front Willwood with racing pads, Rear OEM with Windmax W5. Motul 660 and brake lines.
Wheels: OEM 7 inches with 225/45/17 Federals RR or Falken 615. Tried 245/40/10 on OEM wheels with no better/no worse results.
Suspension: Bilstein B6, Eibach Springs (F 3.6 kg/R 4.9K) and sway bar. Front Camber -3.1 and Rear -2 (fix Pedders and crash bolts). Several (bushings mainly whiteline)
Interior: No mods (only 4 point harness with Hans Device)
Weight reduction: Antigravity YTX12-16 Lithium Battery (OEM died)
Aero: No big aero now or foreseeable future.
Drivability: Street Legal Track Car (do not have trailer)

A year ago, we bought with some friends a Miata NA 94 spec, for endurance racing. We did two races with Champs Car and one with Lemons this year. Surprisingly we won at Harris Hill with Champs Car…because is endurance.

Here is the my confusion,

Miata is a race prep car, old one but well sorted it out. I love the feeling and is helping me to improve a lot my driving. When I track my Scion, it feels very soft, I started not to enjoying it ,not feeling comfortable, and confuse trying to drive it like I do with the Miata.
My times with the SCION are worsening or not improving, time laps with Miata are improving.

So I wandering how much firmer need to be the suspension without having a solid rock car. I need to bring some of the joy of the Miata (without losing AC, stereo and drivability on weekends)

If go with Yellow Spring (F 4.5k, R4.5K) or Sports SPEC-R (F 4.4k, R 5.3K) with my current shocks (B6). Am I going to feel a big improvement against Eibach (F 3.6 kg/R 4.9K)?
Do I need to go Coil Overs with 6K springs (like Tein CGC spec or Racecom Superstreet-1) or do I need to go over 6K spring rates, like Racecomp Tarmac 2 (7.1K F&R)

I need some light here.

Thanks

Picture at MSR Houston Dec '20