A chip will give the optimum fuel and ignition advance curves for best performance on the street and strip,much more than the factory can do. Also part throttle response is improved,even when the Bullitt is stock. Look at it this way,Back in 1968-69,a popular trick was to take the car to a good shop for a dyno tune. This included parts and time for rejetting the carb,reworking the distributor,and plugs and better wires. The cost for this then was about $100 bucks,and gave a good 25-50 HP increase,based on the engine type and state of factory tune. So now 33 yrs. later it will cost you about $280-$365 bucks,not too bad! However those big gains,as seen then,are hard to come by,as todays engines are more efficient. But I think it is worth it,regardless of mods.Hey it is the only way to tune it!