There are many ways in which you can increase the power in your engine, one being that you force more air into the cylinders, to do this you use a turbo, as the exhaust gasses leave the valves they travel through to the turbo charger, as they flow pass the fins they turn, the get faster and fater and they are on a shaft which is conected to more fins which then clows air at an increased rate, however the compressed air is hot which doesent help so it flows throug an intercooler which air passes and then cools the compressd air down as it travels into the cylinder with more fuel. more air means bigger compression so there is more explosion, therefore more power.
If your thinking of a turbo conversion, you have to think of uprgrading:
Conrods and pistons,
Cams and pulleys ( not essential)
Size of turbo as a smaller turbo will give more power at lower revs
spark plugs and lead
bottem end, sleved
anda bit more