Newly calibrated powertrain control module mapping resulted in better drivability, fuel efficiency and emission performance. This improved throttle response, drivability and fuel consumption. However, the V8-6-4 engine would experience problems in drivability and reliability related to cylinder deactivation. These carburetors allowed for very good drivability and fuel efficiency. The system improved the drivability of the Jeep Cherokee and Comanche over carbureted models. Changes to the fuel system improved drivability, economy and emission control. These were very weak sellers, offering much less torque and drivability than their two-cycle brethren. Finally, there are numerous smaller upgrades to vision and ergonomics to improve drivability. Cross-drive transmissions also improved the drivability of the manual transmissions then in use. However, the engine did have increased drivability. This is the same engine as A/C equipped 68 Hurst Olds' and provided better drivability. A trotter's disposition is evaluated during the drivability test. The general drivability test is performed by trotter stallions. Both sexes are also required to pass either a drivability or a ridability test. Drivability is the vehicle's response to general driving conditions.