YS Engines makes all of the larger 4 strokes they offer both turbocharged and fuel injected. At or below 2000 rpm the fuel is drawn from the tank as any normal engine. Above 2000 rpm the fuel is then injected directly to the engine.

The big box on the back of the engine is the "Air Chamber" which pressurizes the air charge to the carb.

All of this works using crankcase pressure so the engine must be turned over at least 10 revolutions before it will start so that pressure can be built in the system.

I have had a YS91AC installed on a CG Ultimate and it had gobs of power [X(]. I have since replaced it with the YS110FZ and what an increase in power.

I also have a Saito 120 that does not put out this amount of power. YS does this while turning large props in the 8800 to 9500 rpm range which is the recommended operating range for these engines.

As far as aftermarket turbo/supercharges. I have never seen anything on them, sorry