If you use the Audio loader included with FLA then try this sound out. It's a decent attempt at replicating the sound of the real 037.

Replace the HATCHBACK_2 sound file in pc>audio>Sfx>STREAMED_VEHICLES.rpf with the one provided, then simply copy this line to the audio loader ini file when you have added the vehicle.

Note that this will alter the sound of any vehicle that uses the HATCHBACK_2 sound file, such as the Landstalker and Habanero.

Data Lines:

gtaiv_vehicleAudioSettings.ini

[mesos]
structType = 0
field_1 = 41999
flags = 0x2AA628 
floatAsInt_A = -16.0
floatAsInt_E = 0.0
engineLowSound = VEHICLES_ENGINE_RESIDENT_HATCHBACK_2_ENGINE_LOW
engineHighSound = VEHICLES_ENGINE_RESIDENT_HATCHBACK_2_ENGINE_HIGH
exhaustLowSound = VEHICLES_ENGINE_RESIDENT_HATCHBACK_2_EXHAUST_LOW
exhaustHighSound = VEHICLES_ENGINE_RESIDENT_HATCHBACK_2_EXHAUST_HIGH
revsOffSound = VEHICLES_ENGINE_RESIDENT_HATCHBACK_2_REVS_OFF
field_26 = 640.0
field_2A = 250.0
floatAsInt_2E = 0.0
floatAsInt_32 = 4.0
field_36 = 4000.0
field_3A = 1000.0
floatAsInt_3E = -4.0
floatAsInt_42 = 0.0
field_46 = 440.0
field_4A = 150.0
floatAsInt_4E = 0.0
floatAsInt_52 = 4.0
field_56 = 140.0
field_5A = 60.0
floatAsInt_5E = 4.0
floatAsInt_62 = 4.0
floatAsInt_66 = 1.0
field_6A = 50.0
field_6E = 50.0
floatAsInt_72 = 0.0
floatAsInt_76 = -18.0
engineWaveShape = ENGINE_WAVE_SHAPE
floatAsInt_7E = 0.0
exhaustWaveShape = EXHAUST_WAVE_SHAPE
floatAsInt_86 = 0.0
floatAsInt_multiplier1200_8A = 0.7
floatAsInt_multiplier1200_8E = 1.9
engineIdleLoopSound = VEHICLES_ENGINE_RESIDENT_HATCHBACK_2_ENG_IDLE_LOOP
exhaustIdleLoopSound = VEHICLES_ENGINE_RESIDENT_HATCHBACK_2_EX_IDLE_LOOP
floatAsInt_multiplier1200_9A = -0.166667
floatAsInt_multiplier1200_9E = 0.333333
transmissionSound = VEHICLES_TRANSMISSION_1
floatAsInt_A6 = -8.0
floatAsInt_AA = 4.0
sound_AE = VEHICLES_ENGINE_RESIDENT_NULL_LOOP
floatAsInt_B2 = -8.0
floatAsInt_B6 = -2.0
exhaustPopSound = EX_POPS_MT
airIntakeSound = TURBO_3_WRAP
floatAsInt_multiplier1200_C2 = -0.5
floatAsInt_multiplier1200_C6 = 0.666667
dumpValveSound = NULL_SOUND
startSound = VEHICLES_ENGINE_RESIDENT_HATCHBACK_2_START
hornSound = TURISMO_MULTI_HORN
openSound = VEHICLES_EXTRAS_MUSCLE_CAR_OPEN
closeSound = MUSCLE_DOOR_CLOSE_RND
trunkOpenSound = VEHICLES_EXTRAS_MUSCLE_TRUNK_OPEN
trunkCloseSound = VEHICLES_EXTRAS_MUSCLE_TRUNK_CLOSE
field_E6 = 0.5
suspensionUpSound = SUSPENSION_UP
suspensionDownSound = SUSPENSION_UP
field_F2 = 0.4
field_F6 = 1.0
policeScannerManufacturerSound = NULL_SOUND
policeScannerModelSound = NULL_SOUND
policeScannerVehicleCategorySound = POLICE_SCANNER_VEHICLE_CATEGORY_SPORTS_CAR
gearTransmissionSound = VEHICLES_ENGINE_RESIDENT_GEAR_TRANSMISSION
floatAsInt_multiplier1200_10A = 0.333333
floatAsInt_multiplier1200_10E = 2.16667
floatAsInt_multiplier1200_112 = 1.0
floatAsInt_116 = 0.0
field_11A = 50
floatAsInt_11E = 0.0
floatAsInt_122 = 8.0
floatAsInt_126 = 16.0
jumpLandSound = VEHICLE_JUMP_LAND
field_12E = 31
field_132 = 36
ignitionSound = IGNITION
engineShutDownSound = VEHICLES_ENGINE_RESIDENT_SHUT_DOWN_1
field_13E = 0
field_13F = 0
field_140 = 1
field_141 = 3
indicatorVehicleOn = VEHICLES_EXTRAS_INDICATOR_OLD_CAR_ON
indicatorVehicleOff = VEHICLES_EXTRAS_INDICATOR_OLD_CAR_OFF
engineCoolingFan = ENGINE_COOLING_FAN
handbrakeSound_14E = NULL_SOUND
sound_152 = NULL_SOUND
sound_156 = NULL_SOUND
handbrakeSound_15A = VEHICLES_EXTRAS_SPORTS_HANDBRAKE
field_15E = 0
field_15F = 0
field_160 = 1