de-stroking comes with more problems than it's worth, unless you want to drop major coin. Parts availability would not be a problem, there are many companies willing to make custom pistons and rods. Depending on bike you would be surprised what has already been engineered in boost ready pistons/rods. Cometic in Cleveland will make you any type of head gasket you want. Cams and cam/valve timing will also need to be tweeked to get the most out of boost. Carbs will cause you all kinds of problems...some will completely box them so the pressure is equal on overflows and vents compared to venturi pressure...the engineering for boosting a carb bike is way beyond this thread. Fuel injection makes it much easier. Above you ask about how the exhaust gasses get put back into the motor... The exhaust goes through a turbine and spins a shaft, the exhaust then goes out the tailpipe. The turbine shaft is connected to a compressor which takes fresh air, compresses the air and pressurizes the intake plenum. A waste gate controls how much pressure the plenum provides to the motor. Waste gate can be mechanical or electronic.