Here's a little data replacement I put together for the FSR GR86 Cup. Delete the old data file/folder inside the car (maybe keep them somewhere so you can switch back) and drop these in. There's also a setup file in there, just drop that into any track you like.
Story behind this: I wasn't happy with how the car felt, so I started fiddling with it. Bear in mind, I have no background/experience with this stuff, so it just goes by how I feel in the car. That's also the reason for the setup file. Basically, it's meant to be the all-time-on, default setup.
Anything I've done might work for you with that setup, or it might not. It could work for other setups, I don't know.
A few notes:
I changed mainly the car.ini, drivetrain.ini, setup.ini, suspension.ini and the power.lut
The power data is eyeballed, so definitely too smooth
I'm pretty sure the dampers are f'd up, I stopped toying with them; while driving they feel overdamped but ok(ish) to me.
I think the brakes are on the weak side
Flames and lights n stuff are missing
As for the notes in the UI, they're just a digital post-it for me, to keep track of what I notice being missing/off/wrong. Keep them, disregard them, delete them, whatever.
For me, these changes have turned this car into something I actually enjoy driving. As with anything in here: if you like it, here you have it, if you don't like it, leave it be.
Most importantly, have fun on track!