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To fix the handling, change the AMBULAN handling in handling.meta to this:
<Item type="CHandlingData">
<handlingName>AMBULAN</handlingName>
<fMass value="5500.000000" />
<fInitialDragCoeff value="6.000000" />
<fPercentSubmerged value="80.000000" />
<vecCentreOfMassOffset x="0.000000" y="0.000000" z="0.000000" />
<vecInertiaMultiplier x="1.000000" y="2.000000" z="1.300000" />
<fDriveBiasFront value="0.000000" />
<nInitialDriveGears value="5" />
<fInitialDriveForce value="0.110000" />
<fDriveInertia value="1.000000" />
<fClutchChangeRateScaleUpShift value="1.300000" />
<fClutchChangeRateScaleDownShift value="1.300000" />
<fInitialDriveMaxFlatVel value="100.000000" />
<fBrakeForce value="0.250000" />
<fBrakeBiasFront value="0.600000" />
<fHandBrakeForce value="0.200000" />
<fSteeringLock value="37.000000" />
<fTractionCurveMax value="1.300000" />
<fTractionCurveMin value="1.100000" />
<fTractionCurveLateral value="16.000000" />
<fTractionSpringDeltaMax value="0.150000" />
<fLowSpeedTractionLossMult value="0.000000" />
<fCamberStiffnesss value="0.000000" />
<fTractionBiasFront value="0.460000" />
<fTractionLossMult value="1.000000" />
<fSuspensionForce value="1.400000" />
<fSuspensionCompDamp value="0.700000" />
<fSuspensionReboundDamp value="1.000000" />
<fSuspensionUpperLimit value="0.150000" />
<fSuspensionLowerLimit value="-0.200000" />
<fSuspensionRaise value="0.000000" />
<fSuspensionBiasFront value="0.470000" />
<fAntiRollBarForce value="0.300000" />
<fAntiRollBarBiasFront value="0.500000" />
<fRollCentreHeightFront value="0.700000" />
<fRollCentreHeightRear value="0.700000" />
<fCollisionDamageMult value="1.000000" />
<fWeaponDamageMult value="1.000000" />
<fDeformationDamageMult value="0.800000" />
<fEngineDamageMult value="1.500000" />
<fPetrolTankVolume value="65.000000" />
<fOilVolume value="5.000000" />
<fSeatOffsetDistX value="0.200000" />
<fSeatOffsetDistY value="-0.400000" />
<fSeatOffsetDistZ value="0.300000" />
<nMonetaryValue value="25000" />
<strModelFlags>224048</strModelFlags>
<strHandlingFlags>0</strHandlingFlags>
<strDamageFlags>0</strDamageFlags>
<AIHandling>AVERAGE</AIHandling>
<SubHandlingData>
<Item type="NULL" />
<Item type="NULL" />
<Item type="NULL" />
</SubHandlingData>
</Item>