Engine swapping

You tuned up your engine, still not enough power.
For example you tuned your b16a2 engine in Honda EG6, it has 200+ horsepower, it's faster than your friend with his stock K20 in a Type R. But K20 has a lot more potential for tuning, it has a 200hp and more torque in a start and a bigger engine. Your friend will only change exhaust system and tune his ECU and he will again be faster than you.
Engine swap tuners economic problem is that it costs a lot of money right in a start, when originally mounted engine can be tuned step by step, not much money at once.
Engine swap isn't just an engine, it's usually also swap of transmission, ECU, engine mounts accessories, drivetrain and much more. Plus money for mechanic to mount an engine and rest of stuff in your car.
Once you're there, all the hard work is forgotten and nothing can compare with happiness when reving up your monster and feel the power of your completed work.
K20 swap in an EG6: