@Frabyn13 any setting file that you may find in mod archive. I can't remember exact path in GTA IV mod folder, so search for the files vehicles.ide, handling.dat, carcols.dat in the game directory.
Put something like
# This file is custom
for vehicles and carcols
and
; This file is custom
for handling in the beginning of file, run the game, and after that check if those marks are still there. If they disappear - that's the nasty work of your launcher.