HERE IS SOME QUICK PROS & CONS.
injection with the computer keeps a better handle on fuel ratio. so it has a better chance to give you better fuel mileage.
on the newer cars, it performs better than there carb counter part.
it will have less emissions
CONS
if your going to inject and old car. you'll have to do alot of wiring, put an O2 sensor in the exhaust pipe,
have to upgrade the fuel system by installing a injection fuel pump,special fuel hose to handle the pressure,and a return line to the tank.
THIS ONE I'M NOT SURE ABOUT...IF YOU USE AN AFTERMARKET INJECTION KIT..YOU MIGHT NEED A SPECIAL TOOL FOR THAT SYSTEM, TO READ THE CODES IN THE COMPUTER IF ONE OF THE SENSORS GO BAD.