1]Replace files coquette.wft and coquette.wtd (in \Grand Theft Auto IV\pc\models\cdimages\vehicles.img) for files from archive, with the help OpenIV or SparkIV.

2]Change config (in \Grand Theft Auto IV\common\data\handling.dat)

handling.dat:

COQUETTE     1600.0  7.0   85 0.0 -0.01 -0.35  0.0  5  0.17  1.0 220.0 0.50 0.65 0.7  35.0  1.45 1.15 14.0 0.15 0.48  2.0  1.2  1.2  0.10 -0.10 0.0  0.5    1.0 1.0 1.1 1.5  0.0  41000   440010  0   0