A matched turbo for your individual set up is what you want for maximum efficient performance. An example is a turbo that is too big will take too long to spool up, for your rpm limit, and you won’t spend enough of your rpm curve under the full power potential that you could be at.
You can also have a turbo that is too small as well, and then you just won’t have enough turbo to get your car where you want. One more instance is your displacement and motor size. A V8 will need a bigger single turbo than a 4 cylinder, due to all the extra air that flows through, and it may need a lot less boost or psi.
This is where you will either want to speak with a turbo kit specialist shop or tuner, and find out if you don’t already know the right match up for your car.
Once you have figured out the correct turbo size, then you will need to decide on the right supporting components, such as the exhaust manifold, correctly fitter intercooler andd intercooler piping, fuel set up, clutch to handle the power to handle it. This is something you will want to research. You will not have to use up all of the potential power of the turbo if you have any limitation, such as the clutch, but ideally for max performance, you will need to match the supporting mods with your goals.
Either do some heavy research on a forum devoted to your car, or contact a shop that carries and knows about turbo kits.
Some people have an extensive knowledge of cars and can easily spot mechanical problems. Some people don’t know anything, especially about prices. If the second group is where you fall, you will find help here. Look online for a great deal.