i leave it on 1.0 enertia for Cars
But when you like it increase enertia do it 
it works for every car, addon or stock....
and take a look on this
vecInertiaMultiplier
EXAMPLE
if you set x="2.000000" it feels like controller damping for left and
right turns
if you set y="2.000000" it feels like the car is longer
if you set z="2.500000" it feels the car get more high
(when the car spin out, feels more realistic)
<fInitialDragCoeff value="5.00000" />
First set this between 4.00000 and 7.000000
<fInitialDriveForce value="0.380000" />
second set this between 0.350000 and 0.450000
<fInitialDriveMaxFlatVel value="245.000000" />
third set this between 200. and 250
<fClutchChangeRateScaleUpShift value="4.500000" /> <fClutchChangeRateScaleDownShift value="4.500000" />
and this set between 1.8 and 4.5
1.8 is like manual shifting
4.5 is double clutch gearbox
dont set it to 7 or 8 it make accel to much
fInitialDragCoeff
but this is very important, if you leave it on 10.00000
the car doesnt reach never 300kmh
Hy..!! what car? Addon or stock
Hy!
Maybe y have Enable "leave engine running" in trainer
What Car..? and give me your email..
You should use "mods" folder...
It is a very good discription on this site..!!!
Take 20 silent minutes and read exatly about "mods" folder
hy!
when you have crash while entering, should be the fail in handling.meta or vehicles.meta
Hy!!
Check your Launcher.log file, you found here..
C:\Users\User\Documents\Rockstar Games\GTA V
and look for Fail Codes Example "107"
you have to update your Social Club Launcher and
Game Launcher Manual...
Take a look on Rockstar Support Homepage, good discription how you do it
hy!!
you can try deinstall sc-launcher,
and manual install..
for 100% correct de- and install visit Rockstar SC Support homepage and search for "social club launcher"
Hy!!
When you remove mod folder, the game works fine?
And what kind of crash you get?
Example: Frozzen Screen and 10 sec noise in speakers
@Ned228
Hy..!! Take a look in your launcher.log file....
You found here:
C:\Users\User\Documents\Rockstar Games\GTA V
Look for ERROR or FAIL CODE example: 107