Don't know if you remember the San Andreas V8 Rumble mod?. Never mind. Heres the GTA4 version.

The idea is to improve a lot of the NORMAL vehicle sounds. Its not a '69 Charger or a Lamborghini Aventador sound mod. 23 Vehicles have overhauled sounds. These are smooth, powerful V8 motor sounds. Not like the buzzy, whiny nonsense Rockstar cobbled together. This is meant for 80s sedans, vintage coupes, and 70s cruisers. Slip it into drive, and roll on the power.

V_STYLE_2 - Buccaneer, Merit, Police2, Taxi2, Virgo,
V_STYLE_4 - Esperanto, Manana, Premier, Romans Taxi, Uranus,
REGULAR_SALOON_1 - Marbella, Willard,
LUXURY_CAR_1 - Feroci, Feroci2, Huntley, Oracle, Presidente, Primo, Vincent,
MUSCLE_CAR_2 - Noose Patriot, Patriot, Peyote, Voodoo,

Installation instructions in README.
Video and support topic on GTAFORUMS.
http://gtaforums.com/topic/782964-reliv-gta-iv-real-v8-rumble/
https://youtu.be/UzRCV_tgZ_M