Engine Computer

If your 83 mustang was bought in it's stock form , I would think it would just have the ignition "box" ( on the fender , about the size of 2 cigarette packs put together) . If the car has been modified , as most are , it could have possably been switched to electronic fuel injection . The easist way to tell is to look at the motor and see if you have a 4 bbl carb , or a big aluminum intake plenum . If the car is stock , my suggestion is to purchase an upgrade kit ( comes with better cam , better intake , lifters , etc ) Edelbrock , Crane , and other big names have kits to help boost performance and you will not need to do any computer upgrades ( no computer in 83 with 4 bbl carb) I do suggest you tear down the motor and have it properly rebuilt . If it is original , it might have had a hard life , and when you do an upgrade , it is a good idea to make sure the motor can take the extra strain of an upgrade . If your car is an automatic , you can only go so far in upgrading the motor before you will need to do the trans . the same goes if you have a standard transmission , but , you can go with a higher lift cam in it and not worry about a "rough" idle as much . Usually you need to think about the car from front to back , when it comes to upgrades , as doing something to one thing will affect others . As long as you don't go too crazy , a mild build up will give good performance and reliability.