Add Cars Tool

Add Cars Tool is a set of files that help not replace, but add vehicles to GTA 4.

Adding transport:

1. Download any car. Pull out the texture and model from the archive.
2. Rename the files you pulled out to any name that is not used in GTA 4. (Example: lexus)
3. Add carcols settings to GTAIV/common/data/addcarcols.dat
4. Add handling settings to GTAIV/common/data/addhandling.dat
5. Add vehicle settings to GTAIV/common/data/addvehicles.ide
   We're done installing the car.

How to find installed transport?
So that you don’t have to run for half an hour, don’t look for the added car (or motorcycle, or whatever you added there), in Simple Native Trainer (for example, let’s take version 5.2) open the trainer.ini file (with a regular notepad).
Press Ctrl+F, in the "What:" field enter: Added Cars and click "Find Next",
scroll down a little. You will see something like this:

Let's take

In the line ModelName1=turismo, replace turismo with the name of the model that you added
(eg acura).
In the line DisplayName1=Car 1, Car 1 we replace it with (for this example) Lexus (you can use both lexus and LEXUS, as is convenient for you). This is the name that will be displayed when this car spawns.

It seems like everything, save, exit and go play, press F3 in the game (the F4 key only minimizes and expands the trainer, unless, of course, you reassigned the control keys). Select Car Spawning, in the menu that opens go to the last page (usually scroll through Num 4 and Num 6), see the “Added Cars” section, and there we see our Lexus (or what you added).

How to remove Add Cars Tool?
Find the ACt_Uninstall file in the game folder. Launch it and click Uninstall.
Then copy all the files from the Backup Files folder in the archive to GTA IV/common/data