What is the maximum practical power difference using turbo and inter-cooler?

If you just turbo the engine, you will get some good power. However, adding an intercooler will not only add horsepower for the same amount of boost as the non intercooled, but you can crank the boost higher (assuming your engine can hold it.) Cold air is more dense, which means you can get more in the cylinders. Intercooler cools the air, allowing more in the cylinders, therefore forcing more fuel, and creating more combustion. The amount depends on numerous factors, including how big the intercooler is, whether you have NO2 spray on the intercooler, etc.|||What he said lol