after doing more research for this car top speed with electric limiter is about 190km i also find acceleration data and top speed with car unlocked (no electric limiter) its no more then 226km / 140mph , i also tested the car in game top speed and your right it does go a lot more then what it should be i manage to get 260km on stock setup and oem gear ratios, so i will consider updating the car giving it little more drag it may not going to be perfect but there has to be a sweet spot that we all agree on.
also if there is app or insim server that allow acceleration display to show times of acceleration so i can do more testing to get it near to "irl" that will be very helpful.
we know irl this car has :
Drag coefficient Cd claimed: 0.27
Frontal area A estimated: 1.94 m²
rear factory wing there are not so much to generate downforce as rather to prevent lift and to not cause lot of drag, and so choose not to use downforce at all, it does the job similar to XRT rear wing/spoiler.
with a simple calculation its possible to get correct results it may not fit perfect in lfs but its irl values.
Fd= cd(1/2(p x v(m/s)² x A
cd = 0.27
p=1.204 by (default natural temp)
v(m/s)= speed witch is optional (i usually use 27.8 cuz it equal 100km) but we can use 40m/ for this example
A= 1.94
knowing all info needed the rest is simple :
fd= 0.27(0.5(1.204 x 40²)1.94
fd=504.52 (N) > my mod has 506 cuz i calculate using 27.8 = 100km but nearly same result.
to get this value in editor i set body drag to 0.316 N @ 1 m/s and double value for side drag as default lfs cars do.
body lift kept it at 0.
what your saying could be right but when i increase aero drag until it's around 240km/h the body drag got 0.433 N @ 1 m/s and has aero drag of 693N @ 40m/s and thats huge and effect acceleration of car making it slower then what it should be.